21180916 has 12 divisors (see below), whose sum is σ = 37231488. Its totient is φ = 10543352.

The previous prime is 21180893. The next prime is 21180917. The reversal of 21180916 is 61908112.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21180917) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10756 + ... + 12571.

It is an arithmetic number, because the mean of its divisors is an integer number (3102624).

Almost surely, 2^21180916 is an apocalyptic number.

It is an amenable number.

21180916 is a deficient number, since it is larger than the sum of its proper divisors (16050572).

21180916 is a wasteful number, since it uses less digits than its factorization.

21180916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23558 (or 23556 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 21180916 is about 4602.2729167228. The cubic root of 21180916 is about 276.6824287402.

The spelling of 21180916 in words is "twenty-one million, one hundred eighty thousand, nine hundred sixteen".