21723136 has 24 divisors (see below), whose sum is σ = 43439760. Its totient is φ = 10860544.

The previous prime is 21723113. The next prime is 21723167. The reversal of 21723136 is 63132712.

It is a self number, because there is not a number n which added to its sum of digits gives 21723136.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3256 + ... + 7351.

It is an arithmetic number, because the mean of its divisors is an integer number (1809990).

Almost surely, 2^21723136 is an apocalyptic number.

It is an amenable number.

21723136 is a deficient number, since it is larger than the sum of its proper divisors (21716624).

21723136 is an equidigital number, since it uses as much as digits as its factorization.

21723136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10629 (or 10609 counting only the distinct ones).

The product of its digits is 1512, while the sum is 25.

The square root of 21723136 is about 4660.8085135521. The cubic root of 21723136 is about 279.0235374515.

Adding to 21723136 its reverse (63132712), we get a palindrome (84855848).

The spelling of 21723136 in words is "twenty-one million, seven hundred twenty-three thousand, one hundred thirty-six".