20721164 has 12 divisors (see below), whose sum is σ = 38395224. Its totient is φ = 9751104.

The previous prime is 20721163. The next prime is 20721209. The reversal of 20721164 is 46112702.

It is not an unprimeable number, because it can be changed into a prime (20721161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 152294 + ... + 152429.

It is an arithmetic number, because the mean of its divisors is an integer number (3199602).

Almost surely, 2^20721164 is an apocalyptic number.

It is an amenable number.

20721164 is a deficient number, since it is larger than the sum of its proper divisors (17674060).

20721164 is a wasteful number, since it uses less digits than its factorization.

20721164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304744 (or 304742 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 20721164 is about 4552.0505269603. The cubic root of 20721164 is about 274.6658818224.

Adding to 20721164 its reverse (46112702), we get a palindrome (66833866).

The spelling of 20721164 in words is "twenty million, seven hundred twenty-one thousand, one hundred sixty-four".