21261040 has 40 divisors (see below), whose sum is σ = 51032448. Its totient is φ = 8229120.

The previous prime is 21261029. The next prime is 21261041. The reversal of 21261040 is 4016212.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261041) 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 7 ways as a sum of consecutive naturals, for example, 1807 + ... + 6766.

Almost surely, 2^21261040 is an apocalyptic number.

21261040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21261040 is an abundant number, since it is smaller than the sum of its proper divisors (29771408).

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

21261040 is a wasteful number, since it uses less digits than its factorization.

21261040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8617 (or 8611 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 21261040 is about 4610.9695292856. The cubic root of 21261040 is about 277.0308714566.

Adding to 21261040 its reverse (4016212), we get a palindrome (25277252).

The spelling of 21261040 in words is "twenty-one million, two hundred sixty-one thousand, forty".