21209164 has 12 divisors (see below), whose sum is σ = 37150288. Its totient is φ = 10594800.

The previous prime is 21209161. The next prime is 21209171. The reversal of 21209164 is 46190212.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21209161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4849 + ... + 8119.

Almost surely, 2^21209164 is an apocalyptic number.

It is an amenable number.

21209164 is a deficient number, since it is larger than the sum of its proper divisors (15941124).

21209164 is a wasteful number, since it uses less digits than its factorization.

21209164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4896 (or 4894 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21209164 is about 4605.3408125784. The cubic root of 21209164 is about 276.8053735856.

Adding to 21209164 its reverse (46190212), we get a palindrome (67399376).

The spelling of 21209164 in words is "twenty-one million, two hundred nine thousand, one hundred sixty-four".