21939399 has 12 divisors (see below), whose sum is σ = 32783400. Its totient is φ = 14121744.

The previous prime is 21939391. The next prime is 21939419. The reversal of 21939399 is 99393912.

It is not a de Polignac number, because 21939399 - 2³ = 21939391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21939391) 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 11 ways as a sum of consecutive naturals, for example, 41769 + ... + 42290.

It is an arithmetic number, because the mean of its divisors is an integer number (2731950).

Almost surely, 2^21939399 is an apocalyptic number.

21939399 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21939399 is a deficient number, since it is larger than the sum of its proper divisors (10844001).

21939399 is a wasteful number, since it uses less digits than its factorization.

21939399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84094 (or 84091 counting only the distinct ones).

The product of its digits is 118098, while the sum is 45.

The square root of 21939399 is about 4683.9512166546. The cubic root of 21939399 is about 279.9464140652.

The spelling of 21939399 in words is "twenty-one million, nine hundred thirty-nine thousand, three hundred ninety-nine".