21636736 has 64 divisors (see below), whose sum is σ = 47784960. Its totient is φ = 9757440.

The previous prime is 21636709. The next prime is 21636743. The reversal of 21636736 is 63763612.

It is a tau number, because it is divible by the number of its divisors (64).

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, 170305 + ... + 170431.

It is an arithmetic number, because the mean of its divisors is an integer number (746640).

Almost surely, 2^21636736 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 21636736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23892480).

21636736 is an abundant number, since it is smaller than the sum of its proper divisors (26148224).

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

21636736 is an equidigital number, since it uses as much as digits as its factorization.

21636736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174 (or 140 counting only the distinct ones).

The product of its digits is 27216, while the sum is 34.

The square root of 21636736 is about 4651.5305008137. The cubic root of 21636736 is about 278.6531233800.

The spelling of 21636736 in words is "twenty-one million, six hundred thirty-six thousand, seven hundred thirty-six".