20726991 has 6 divisors (see below), whose sum is σ = 29939000. Its totient is φ = 13817988.

The previous prime is 20726971. The next prime is 20727023. The reversal of 20726991 is 19962702.

It is not a de Polignac number, because 20726991 - 2⁹ = 20726479 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 (20726921) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 1151491 + ... + 1151508.

Almost surely, 2^20726991 is an apocalyptic number.

20726991 is a deficient number, since it is larger than the sum of its proper divisors (9212009).

20726991 is a wasteful number, since it uses less digits than its factorization.

20726991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2303005 (or 2303002 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The square root of 20726991 is about 4552.6905231961. The cubic root of 20726991 is about 274.6916256801.

The spelling of 20726991 in words is "twenty million, seven hundred twenty-six thousand, nine hundred ninety-one".