21139990 has 32 divisors (see below), whose sum is σ = 40124160. Its totient is φ = 8003424.

The previous prime is 21139981. The next prime is 21139999. The reversal of 21139990 is 9993112.

It is an interprime number because it is at equal distance from previous prime (21139981) and next prime (21139999).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21139999) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24181 + ... + 25039.

It is an arithmetic number, because the mean of its divisors is an integer number (1253880).

Almost surely, 2^21139990 is an apocalyptic number.

21139990 is a deficient number, since it is larger than the sum of its proper divisors (18984170).

21139990 is a wasteful number, since it uses less digits than its factorization.

21139990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 996.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 21139990 is about 4597.8244855584. The cubic root of 21139990 is about 276.5041108927.

The spelling of 21139990 in words is "twenty-one million, one hundred thirty-nine thousand, nine hundred ninety".