21399942 has 16 divisors (see below), whose sum is σ = 42845760. Its totient is φ = 7125672.

The previous prime is 21399929. The next prime is 21399943. The reversal of 21399942 is 24999312.

It is a self number, because there is not a number n which added to its sum of digits gives 21399942.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21399943) 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, 8613 + ... + 10815.

It is an arithmetic number, because the mean of its divisors is an integer number (2677860).

Almost surely, 2^21399942 is an apocalyptic number.

21399942 is an abundant number, since it is smaller than the sum of its proper divisors (21445818).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21399942 is a wasteful number, since it uses less digits than its factorization.

21399942 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3827.

The product of its digits is 34992, while the sum is 39.

The square root of 21399942 is about 4626.0071335872. The cubic root of 21399942 is about 277.6328590331.

The spelling of 21399942 in words is "twenty-one million, three hundred ninety-nine thousand, nine hundred forty-two".