21356736 has 56 divisors (see below), whose sum is σ = 57905904. Its totient is φ = 6942720.

The previous prime is 21356723. The next prime is 21356759. The reversal of 21356736 is 63765312.

It is a super-2 number, since 2×21356736² = 912220345147392, which contains 22 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21356697 and 21356706.

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, 6516 + ... + 9228.

It is an arithmetic number, because the mean of its divisors is an integer number (1034034).

Almost surely, 2^21356736 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21356736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28952952).

21356736 is an abundant number, since it is smaller than the sum of its proper divisors (36549168).

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

21356736 is a wasteful number, since it uses less digits than its factorization.

21356736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2769 (or 2759 counting only the distinct ones).

The product of its digits is 22680, while the sum is 33.

The square root of 21356736 is about 4621.3348720905. The cubic root of 21356736 is about 277.4458883209.

The spelling of 21356736 in words is "twenty-one million, three hundred fifty-six thousand, seven hundred thirty-six".