21086978 has 8 divisors (see below), whose sum is σ = 34506000. Its totient is φ = 9584980.

The previous prime is 21086971. The next prime is 21086981. The reversal of 21086978 is 87968012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21086971) 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, 479228 + ... + 479271.

It is an arithmetic number, because the mean of its divisors is an integer number (4313250).

Almost surely, 2^21086978 is an apocalyptic number.

21086978 is a deficient number, since it is larger than the sum of its proper divisors (13419022).

21086978 is a wasteful number, since it uses less digits than its factorization.

21086978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 958512.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21086978 is about 4592.0559665579. The cubic root of 21086978 is about 276.2727909235.

The spelling of 21086978 in words is "twenty-one million, eighty-six thousand, nine hundred seventy-eight".