21507916 has 6 divisors (see below), whose sum is σ = 37638860. Its totient is φ = 10753956.

The previous prime is 21507911. The next prime is 21507931. The reversal of 21507916 is 61970512.

It is not an unprimeable number, because it can be changed into a prime (21507911) 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, 2688486 + ... + 2688493.

Almost surely, 2^21507916 is an apocalyptic number.

It is an amenable number.

21507916 is a deficient number, since it is larger than the sum of its proper divisors (16130944).

21507916 is a wasteful number, since it uses less digits than its factorization.

21507916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5376983 (or 5376981 counting only the distinct ones).

The product of its (nonzero) digits is 3780, while the sum is 31.

The square root of 21507916 is about 4637.6627734237. The cubic root of 21507916 is about 278.0990106759.

The spelling of 21507916 in words is "twenty-one million, five hundred seven thousand, nine hundred sixteen".