21991358 has 16 divisors (see below), whose sum is σ = 34615296. Its totient is φ = 10458360.

The previous prime is 21991349. The next prime is 21991397. The reversal of 21991358 is 85319912.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7535 + ... + 10037.

It is an arithmetic number, because the mean of its divisors is an integer number (2163456).

Almost surely, 2^21991358 is an apocalyptic number.

21991358 is a deficient number, since it is larger than the sum of its proper divisors (12623938).

21991358 is a wasteful number, since it uses less digits than its factorization.

21991358 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2719.

The product of its digits is 19440, while the sum is 38.

The square root of 21991358 is about 4689.4944290403. The cubic root of 21991358 is about 280.1672385272.

The spelling of 21991358 in words is "twenty-one million, nine hundred ninety-one thousand, three hundred fifty-eight".