21372736 has 56 divisors (see below), whose sum is σ = 52888896. Its totient is φ = 8325120.

The previous prime is 21372719. The next prime is 21372737. The reversal of 21372736 is 63727312.

It is a tau number, because it is divible by the number of its divisors (56).

It is a junction number, because it is equal to n+sod(n) for n = 21372698 and 21372707.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21372737) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2760 + ... + 7096.

Almost surely, 2^21372736 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 21372736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26444448).

21372736 is an abundant number, since it is smaller than the sum of its proper divisors (31516160).

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

21372736 is a wasteful number, since it uses less digits than its factorization.

21372736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4367 (or 4357 counting only the distinct ones).

The product of its digits is 10584, while the sum is 31.

The square root of 21372736 is about 4623.0656495447. The cubic root of 21372736 is about 277.5151564916.

It can be divided in two parts, 2 and 1372736, that multiplied together give a palindrome (2745472).

The spelling of 21372736 in words is "twenty-one million, three hundred seventy-two thousand, seven hundred thirty-six".