21109986 has 12 divisors (see below), whose sum is σ = 45738342. Its totient is φ = 7036656.

The previous prime is 21109973. The next prime is 21109987. The reversal of 21109986 is 68990112.

It can be written as a sum of positive squares in only one way, i.e., 19633761 + 1476225 = 4431^2 + 1215^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21109986.

It is not an unprimeable number, because it can be changed into a prime (21109987) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 586371 + ... + 586406.

Almost surely, 2^21109986 is an apocalyptic number.

21109986 is an abundant number, since it is smaller than the sum of its proper divisors (24628356).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21109986 is a wasteful number, since it uses less digits than its factorization.

21109986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1172785 (or 1172782 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21109986 is about 4594.5604795236. The cubic root of 21109986 is about 276.3732348076.

The spelling of 21109986 in words is "twenty-one million, one hundred nine thousand, nine hundred eighty-six".