21999986 has 16 divisors (see below), whose sum is σ = 35259360. Its totient is φ = 10264320.

The previous prime is 21999977. The next prime is 22000001. The reversal of 21999986 is 68999912.

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, 1775 + ... + 6866.

It is an arithmetic number, because the mean of its divisors is an integer number (2203710).

Almost surely, 2^21999986 is an apocalyptic number.

21999986 is a deficient number, since it is larger than the sum of its proper divisors (13259374).

21999986 is a wasteful number, since it uses less digits than its factorization.

21999986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8729.

The product of its digits is 629856, while the sum is 53.

The square root of 21999986 is about 4690.4142674182. The cubic root of 21999986 is about 280.2038736283.

The spelling of 21999986 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred eighty-six".