21939986 has 16 divisors (see below), whose sum is σ = 33701184. Its totient is φ = 10708464.

The previous prime is 21939977. The next prime is 21939997. The reversal of 21939986 is 68993912.

It is a self number, because there is not a number n which added to its sum of digits gives 21939986.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27485 + ... + 28271.

It is an arithmetic number, because the mean of its divisors is an integer number (2106324).

Almost surely, 2^21939986 is an apocalyptic number.

21939986 is a deficient number, since it is larger than the sum of its proper divisors (11761198).

21939986 is a wasteful number, since it uses less digits than its factorization.

21939986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1105.

The product of its digits is 209952, while the sum is 47.

The square root of 21939986 is about 4684.0138770076. The cubic root of 21939986 is about 279.9489107468.

The spelling of 21939986 in words is "twenty-one million, nine hundred thirty-nine thousand, nine hundred eighty-six".