20931399 has 8 divisors (see below), whose sum is σ = 31009520. Its totient is φ = 13954248.

The previous prime is 20931389. The next prime is 20931401. The reversal of 20931399 is 99313902.

It is not a de Polignac number, because 20931399 - 2⁵ = 20931367 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 (20931349) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 387592 + ... + 387645.

It is an arithmetic number, because the mean of its divisors is an integer number (3876190).

Almost surely, 2^20931399 is an apocalyptic number.

20931399 is a deficient number, since it is larger than the sum of its proper divisors (10078121).

20931399 is an equidigital number, since it uses as much as digits as its factorization.

20931399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 775246 (or 775240 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 36.

The square root of 20931399 is about 4575.0845893819. The cubic root of 20931399 is about 275.5916693464.

The spelling of 20931399 in words is "twenty million, nine hundred thirty-one thousand, three hundred ninety-nine".