21499988 has 24 divisors (see below), whose sum is σ = 39325440. Its totient is φ = 10272960.

The previous prime is 21499981. The next prime is 21500021. The reversal of 21499988 is 88999412.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21499981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9248 + ... + 11336.

It is an arithmetic number, because the mean of its divisors is an integer number (1638560).

Almost surely, 2^21499988 is an apocalyptic number.

It is an amenable number.

21499988 is a deficient number, since it is larger than the sum of its proper divisors (17825452).

21499988 is a wasteful number, since it uses less digits than its factorization.

21499988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2207 (or 2205 counting only the distinct ones).

The product of its digits is 373248, while the sum is 50.

The square root of 21499988 is about 4636.8079537544. The cubic root of 21499988 is about 278.0648365930.

The spelling of 21499988 in words is "twenty-one million, four hundred ninety-nine thousand, nine hundred eighty-eight".