21309136 has 10 divisors (see below), whose sum is σ = 41286482. Its totient is φ = 10654560.

The previous prime is 21309133. The next prime is 21309179. The reversal of 21309136 is 63190312.

It can be written as a sum of positive squares in only one way, i.e., 11424400 + 9884736 = 3380^2 + 3144^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21309136.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21309133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665895 + ... + 665926.

Almost surely, 2^21309136 is an apocalyptic number.

It is an amenable number.

21309136 is a deficient number, since it is larger than the sum of its proper divisors (19977346).

21309136 is a wasteful number, since it uses less digits than its factorization.

21309136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1331829 (or 1331823 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 25.

The square root of 21309136 is about 4616.1819721497. The cubic root of 21309136 is about 277.2396107330.

Adding to 21309136 its reverse (63190312), we get a palindrome (84499448).

The spelling of 21309136 in words is "twenty-one million, three hundred nine thousand, one hundred thirty-six".