20399791 has 4 divisors (see below), whose sum is σ = 20687184. Its totient is φ = 20112400.

The previous prime is 20399773. The next prime is 20399807. The reversal of 20399791 is 19799302.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19799302 = 2 ⋅9899651.

It is a cyclic number.

It is not a de Polignac number, because 20399791 - 2⁹ = 20399279 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 (20309791) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143590 + ... + 143731.

It is an arithmetic number, because the mean of its divisors is an integer number (5171796).

Almost surely, 2^20399791 is an apocalyptic number.

20399791 is a deficient number, since it is larger than the sum of its proper divisors (287393).

20399791 is an equidigital number, since it uses as much as digits as its factorization.

20399791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287392.

The product of its (nonzero) digits is 30618, while the sum is 40.

The square root of 20399791 is about 4516.6127795063. The cubic root of 20399791 is about 273.2385084846.

The spelling of 20399791 in words is "twenty million, three hundred ninety-nine thousand, seven hundred ninety-one".