21645164 has 6 divisors (see below), whose sum is σ = 37879044. Its totient is φ = 10822580.

The previous prime is 21645133. The next prime is 21645167. The reversal of 21645164 is 46154612.

It is not an unprimeable number, because it can be changed into a prime (21645167) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2705642 + ... + 2705649.

It is an arithmetic number, because the mean of its divisors is an integer number (6313174).

Almost surely, 2^21645164 is an apocalyptic number.

It is an amenable number.

21645164 is a deficient number, since it is larger than the sum of its proper divisors (16233880).

21645164 is a wasteful number, since it uses less digits than its factorization.

21645164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5411295 (or 5411293 counting only the distinct ones).

The product of its digits is 5760, while the sum is 29.

The square root of 21645164 is about 4652.4363509886. The cubic root of 21645164 is about 278.6892992563.

Adding to 21645164 its reverse (46154612), we get a palindrome (67799776).

It can be divided in two parts, 21645 and 164, that multiplied together give a triangular number (3549780 = T₂₆₆₄).

The spelling of 21645164 in words is "twenty-one million, six hundred forty-five thousand, one hundred sixty-four".