21381986 has 8 divisors (see below), whose sum is σ = 32236380. Its totient is φ = 10636528.

The previous prime is 21381979. The next prime is 21381991. The reversal of 21381986 is 68918312.

It can be written as a sum of positive squares in 2 ways, for example, as 15452761 + 5929225 = 3931^2 + 2435^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26741 + ... + 27528.

Almost surely, 2^21381986 is an apocalyptic number.

21381986 is a deficient number, since it is larger than the sum of its proper divisors (10854394).

21381986 is a wasteful number, since it uses less digits than its factorization.

21381986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54468.

The product of its digits is 20736, while the sum is 38.

The square root of 21381986 is about 4624.0659597372. The cubic root of 21381986 is about 277.5551863839. Note that the first 3 decimals are identical.

The spelling of 21381986 in words is "twenty-one million, three hundred eighty-one thousand, nine hundred eighty-six".