21274640 has 40 divisors (see below), whose sum is σ = 49972248. Its totient is φ = 8422400.

The previous prime is 21274639. The next prime is 21274651. The reversal of 21274640 is 4647212.

It can be written as a sum of positive squares in 4 ways, for example, as 3701776 + 17572864 = 1924^2 + 4192^2 .

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

It is a super-2 number, since 2×21274640² = 905220614259200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6764 + ... + 9396.

Almost surely, 2^21274640 is an apocalyptic number.

21274640 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 21274640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24986124).

21274640 is an abundant number, since it is smaller than the sum of its proper divisors (28697608).

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

21274640 is a wasteful number, since it uses less digits than its factorization.

21274640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2747 (or 2741 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21274640 is about 4612.4440376009. Note that the first 3 decimals coincide. The cubic root of 21274640 is about 277.0899280973.

The spelling of 21274640 in words is "twenty-one million, two hundred seventy-four thousand, six hundred forty".