21138164 has 6 divisors (see below), whose sum is σ = 36991794. Its totient is φ = 10569080.

The previous prime is 21138163. The next prime is 21138179. The reversal of 21138164 is 46183112.

It can be written as a sum of positive squares in only one way, i.e., 10627600 + 10510564 = 3260^2 + 3242^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138163) 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 as a sum of consecutive naturals, namely, 2642267 + ... + 2642274.

It is an arithmetic number, because the mean of its divisors is an integer number (6165299).

Almost surely, 2^21138164 is an apocalyptic number.

It is an amenable number.

21138164 is a deficient number, since it is larger than the sum of its proper divisors (15853630).

21138164 is a wasteful number, since it uses less digits than its factorization.

21138164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5284545 (or 5284543 counting only the distinct ones).

The product of its digits is 1152, while the sum is 26.

The square root of 21138164 is about 4597.6259090970. The cubic root of 21138164 is about 276.4961495038.

The spelling of 21138164 in words is "twenty-one million, one hundred thirty-eight thousand, one hundred sixty-four".