21299988 has 48 divisors (see below), whose sum is σ = 52881920. Its totient is φ = 6653664.

The previous prime is 21299987. The next prime is 21300029. The reversal of 21299988 is 88999212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21299983) 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, 23031 + ... + 23937.

Almost surely, 2^21299988 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21299988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26440960).

21299988 is an abundant number, since it is smaller than the sum of its proper divisors (31581932).

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

21299988 is a wasteful number, since it uses less digits than its factorization.

21299988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1036 (or 1034 counting only the distinct ones).

The product of its digits is 186624, while the sum is 48.

The square root of 21299988 is about 4615.1910036314. The cubic root of 21299988 is about 277.1999321185.

The spelling of 21299988 in words is "twenty-one million, two hundred ninety-nine thousand, nine hundred eighty-eight".