21901986 has 12 divisors (see below), whose sum is σ = 47454342. Its totient is φ = 7300656.

The previous prime is 21901981. The next prime is 21901993. The reversal of 21901986 is 68910912.

It can be written as a sum of positive squares in only one way, i.e., 16524225 + 5377761 = 4065^2 + 2319^2 .

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21901986.

It is not an unprimeable number, because it can be changed into a prime (21901981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 608371 + ... + 608406.

Almost surely, 2^21901986 is an apocalyptic number.

21901986 is an abundant number, since it is smaller than the sum of its proper divisors (25552356).

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

21901986 is a wasteful number, since it uses less digits than its factorization.

21901986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1216785 (or 1216782 counting only the distinct ones).

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

The square root of 21901986 is about 4679.9557690218. The cubic root of 21901986 is about 279.7871937456.

The spelling of 21901986 in words is "twenty-one million, nine hundred one thousand, nine hundred eighty-six".