21572164 has 6 divisors (see below), whose sum is σ = 37751294. Its totient is φ = 10786080.

The previous prime is 21572141. The next prime is 21572179. The reversal of 21572164 is 46127512.

It can be written as a sum of positive squares in only one way, i.e., 21160000 + 412164 = 4600^2 + 642^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2696517 + ... + 2696524.

Almost surely, 2^21572164 is an apocalyptic number.

It is an amenable number.

21572164 is a deficient number, since it is larger than the sum of its proper divisors (16179130).

21572164 is a wasteful number, since it uses less digits than its factorization.

21572164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5393045 (or 5393043 counting only the distinct ones).

The product of its digits is 3360, while the sum is 28.

The square root of 21572164 is about 4644.5843732244. The cubic root of 21572164 is about 278.3756459352.

Adding to 21572164 its reverse (46127512), we get a palindrome (67699676).

It can be divided in two parts, 21572 and 164, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21572164 in words is "twenty-one million, five hundred seventy-two thousand, one hundred sixty-four".