21911986 has 4 divisors (see below), whose sum is σ = 32867982. Its totient is φ = 10955992.

The previous prime is 21911971. The next prime is 21911987. The reversal of 21911986 is 68911912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21911761 + 225 = 4681^2 + 15^2 .

It is not an unprimeable number, because it can be changed into a prime (21911987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5477995 + ... + 5477998.

Almost surely, 2^21911986 is an apocalyptic number.

21911986 is a deficient number, since it is larger than the sum of its proper divisors (10955996).

21911986 is a wasteful number, since it uses less digits than its factorization.

21911986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10955995.

The product of its digits is 7776, while the sum is 37.

The square root of 21911986 is about 4681.0240332645. The cubic root of 21911986 is about 279.8297689749.

The spelling of 21911986 in words is "twenty-one million, nine hundred eleven thousand, nine hundred eighty-six".