21172836 has 24 divisors (see below), whose sum is σ = 49684320. Its totient is φ = 7017472.

The previous prime is 21172829. The next prime is 21172849. The reversal of 21172836 is 63827112.

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, 2781 + ... + 7076.

It is an arithmetic number, because the mean of its divisors is an integer number (2070180).

Almost surely, 2^21172836 is an apocalyptic number.

It is an amenable number.

21172836 is an abundant number, since it is smaller than the sum of its proper divisors (28511484).

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

21172836 is a wasteful number, since it uses less digits than its factorization.

21172836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10043 (or 10041 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 21172836 is about 4601.3950058651. The cubic root of 21172836 is about 276.6472417452.

Adding to 21172836 its reverse (63827112), we get a palindrome (84999948).

The spelling of 21172836 in words is "twenty-one million, one hundred seventy-two thousand, eight hundred thirty-six".