21678986 has 16 divisors (see below), whose sum is σ = 37255680. Its totient is φ = 9268080.

The previous prime is 21678983. The next prime is 21678991. The reversal of 21678986 is 68987612.

It is a self number, because there is not a number n which added to its sum of digits gives 21678986.

It is not an unprimeable number, because it can be changed into a prime (21678983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4775 + ... + 8133.

It is an arithmetic number, because the mean of its divisors is an integer number (2328480).

Almost surely, 2^21678986 is an apocalyptic number.

21678986 is a deficient number, since it is larger than the sum of its proper divisors (15576694).

21678986 is a wasteful number, since it uses less digits than its factorization.

21678986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3829.

The product of its digits is 290304, while the sum is 47.

The square root of 21678986 is about 4656.0698018823. The cubic root of 21678986 is about 278.8343805355.

The spelling of 21678986 in words is "twenty-one million, six hundred seventy-eight thousand, nine hundred eighty-six".