20802991 has 16 divisors (see below), whose sum is σ = 23639040. Its totient is φ = 18139680.

The previous prime is 20802989. The next prime is 20803007. The reversal of 20802991 is 19920802.

It is a cyclic number.

It is not a de Polignac number, because 20802991 - 2¹ = 20802989 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 (20802941) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 31830 + ... + 32476.

It is an arithmetic number, because the mean of its divisors is an integer number (1477440).

Almost surely, 2^20802991 is an apocalyptic number.

20802991 is a deficient number, since it is larger than the sum of its proper divisors (2836049).

20802991 is a wasteful number, since it uses less digits than its factorization.

20802991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 774.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 20802991 is about 4561.0295986762. The cubic root of 20802991 is about 275.0269549336.

The spelling of 20802991 in words is "twenty million, eight hundred two thousand, nine hundred ninety-one".