21991726 has 16 divisors (see below), whose sum is σ = 34538400. Its totient is φ = 10482208.

The previous prime is 21991699. The next prime is 21991733. The reversal of 21991726 is 62719912.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 17280 + ... + 18508.

It is an arithmetic number, because the mean of its divisors is an integer number (2158650).

Almost surely, 2^21991726 is an apocalyptic number.

21991726 is a deficient number, since it is larger than the sum of its proper divisors (12546674).

21991726 is a wasteful number, since it uses less digits than its factorization.

21991726 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1643.

The product of its digits is 13608, while the sum is 37.

The square root of 21991726 is about 4689.5336655152. The cubic root of 21991726 is about 280.1688012769.

The spelling of 21991726 in words is "twenty-one million, nine hundred ninety-one thousand, seven hundred twenty-six".