21188516 has 6 divisors (see below), whose sum is σ = 37079910. Its totient is φ = 10594256.

The previous prime is 21188501. The next prime is 21188527. The reversal of 21188516 is 61588112.

It can be written as a sum of positive squares in only one way, i.e., 20286016 + 902500 = 4504^2 + 950^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2648561 + ... + 2648568.

It is an arithmetic number, because the mean of its divisors is an integer number (6179985).

Almost surely, 2^21188516 is an apocalyptic number.

It is an amenable number.

21188516 is a deficient number, since it is larger than the sum of its proper divisors (15891394).

21188516 is a wasteful number, since it uses less digits than its factorization.

21188516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5297133 (or 5297131 counting only the distinct ones).

The product of its digits is 3840, while the sum is 32.

The square root of 21188516 is about 4603.0985216482. The cubic root of 21188516 is about 276.7155172526.

The spelling of 21188516 in words is "twenty-one million, one hundred eighty-eight thousand, five hundred sixteen".