21986917 has 4 divisors (see below), whose sum is σ = 22581196. Its totient is φ = 21392640.

The previous prime is 21986903. The next prime is 21986953. The reversal of 21986917 is 71968912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19633761 + 2353156 = 4431^2 + 1534^2 .

It is a cyclic number.

It is not a de Polignac number, because 21986917 - 2¹⁹ = 21462629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21986957) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 297084 + ... + 297157.

It is an arithmetic number, because the mean of its divisors is an integer number (5645299).

Almost surely, 2^21986917 is an apocalyptic number.

It is an amenable number.

21986917 is a deficient number, since it is larger than the sum of its proper divisors (594279).

21986917 is an equidigital number, since it uses as much as digits as its factorization.

21986917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594278.

The product of its digits is 54432, while the sum is 43.

The square root of 21986917 is about 4689.0208999321. The cubic root of 21986917 is about 280.1483779901.

The spelling of 21986917 in words is "twenty-one million, nine hundred eighty-six thousand, nine hundred seventeen".