21139988 has 12 divisors (see below), whose sum is σ = 37027200. Its totient is φ = 10560792.

The previous prime is 21139981. The next prime is 21139999. The reversal of 21139988 is 88993112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21139981) 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, 7613 + ... + 10011.

It is an arithmetic number, because the mean of its divisors is an integer number (3085600).

Almost surely, 2^21139988 is an apocalyptic number.

It is an amenable number.

21139988 is a deficient number, since it is larger than the sum of its proper divisors (15887212).

21139988 is a wasteful number, since it uses less digits than its factorization.

21139988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4606 (or 4604 counting only the distinct ones).

The product of its digits is 31104, while the sum is 41.

The square root of 21139988 is about 4597.8242680642. The cubic root of 21139988 is about 276.5041021729.

The spelling of 21139988 in words is "twenty-one million, one hundred thirty-nine thousand, nine hundred eighty-eight".