20402991 has 36 divisors (see below), whose sum is σ = 34905936. Its totient is φ = 11249280.

The previous prime is 20402981. The next prime is 20403007. The reversal of 20402991 is 19920402.

It is not a de Polignac number, because 20402991 - 2⁵ = 20402959 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20402951) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 60375 + ... + 60711.

Almost surely, 2^20402991 is an apocalyptic number.

20402991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

20402991 is a deficient number, since it is larger than the sum of its proper divisors (14502945).

20402991 is a wasteful number, since it uses less digits than its factorization.

20402991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 412 (or 378 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 20402991 is about 4516.9670133841. The cubic root of 20402991 is about 273.2527948649.

The spelling of 20402991 in words is "twenty million, four hundred two thousand, nine hundred ninety-one".