21264540 has 144 divisors (see below), whose sum is σ = 68372640. Its totient is φ = 4928000.

The previous prime is 21264521. The next prime is 21264541. The reversal of 21264540 is 4546212.

It is a super-2 number, since 2×21264540² = 904361322823200, which contains 22 as substring.

It is a plaindrome in base 16.

It is a zygodrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21264540.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 210490 + ... + 210590.

It is an arithmetic number, because the mean of its divisors is an integer number (474810).

Almost surely, 2^21264540 is an apocalyptic number.

21264540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21264540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34186320).

21264540 is an abundant number, since it is smaller than the sum of its proper divisors (47108100).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21264540 is a wasteful number, since it uses less digits than its factorization.

21264540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164 (or 151 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 21264540 is about 4611.3490433928. The cubic root of 21264540 is about 277.0460722629.

It can be divided in two parts, 2126 and 4540, that added together give a palindrome (6666).

The spelling of 21264540 in words is "twenty-one million, two hundred sixty-four thousand, five hundred forty".