21306986 has 4 divisors (see below), whose sum is σ = 31960482. Its totient is φ = 10653492.

The previous prime is 21306983. The next prime is 21306997. The reversal of 21306986 is 68960312.

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., 14707225 + 6599761 = 3835^2 + 2569^2 .

It is not an unprimeable number, because it can be changed into a prime (21306983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5326745 + ... + 5326748.

Almost surely, 2^21306986 is an apocalyptic number.

21306986 is a deficient number, since it is larger than the sum of its proper divisors (10653496).

21306986 is a wasteful number, since it uses less digits than its factorization.

21306986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10653495.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21306986 is about 4615.9490898406. The cubic root of 21306986 is about 277.2302863253.

The spelling of 21306986 in words is "twenty-one million, three hundred six thousand, nine hundred eighty-six".