21540916 has 6 divisors (see below), whose sum is σ = 37696610. Its totient is φ = 10770456.

The previous prime is 21540901. The next prime is 21540917. The reversal of 21540916 is 61904512.

It can be written as a sum of positive squares in only one way, i.e., 13395600 + 8145316 = 3660^2 + 2854^2 .

It is a super-2 number, since 2×21540916² = 928022124238112, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2692611 + ... + 2692618.

Almost surely, 2^21540916 is an apocalyptic number.

It is an amenable number.

21540916 is a deficient number, since it is larger than the sum of its proper divisors (16155694).

21540916 is a wasteful number, since it uses less digits than its factorization.

21540916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5385233 (or 5385231 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21540916 is about 4641.2192363645. The cubic root of 21540916 is about 278.2411688427.

The spelling of 21540916 in words is "twenty-one million, five hundred forty thousand, nine hundred sixteen".