21534440 has 64 divisors (see below), whose sum is σ = 51321600. Its totient is φ = 8115712.

The previous prime is 21534437. The next prime is 21534451. The reversal of 21534440 is 4443512.

It is a super-2 number, since 2×21534440² = 927464212227200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 81749 + ... + 82011.

It is an arithmetic number, because the mean of its divisors is an integer number (801900).

Almost surely, 2^21534440 is an apocalyptic number.

21534440 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 21534440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25660800).

21534440 is an abundant number, since it is smaller than the sum of its proper divisors (29787160).

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

21534440 is a wasteful number, since it uses less digits than its factorization.

21534440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386 (or 382 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 21534440 is about 4640.5215224153. The cubic root of 21534440 is about 278.2132828356.

Adding to 21534440 its reverse (4443512), we get a palindrome (25977952).

The spelling of 21534440 in words is "twenty-one million, five hundred thirty-four thousand, four hundred forty".