21239900 has 36 divisors (see below), whose sum is σ = 50283240. Its totient is φ = 7723200.

The previous prime is 21239899. The next prime is 21239903. The reversal of 21239900 is 993212.

It is a super-2 number, since 2×21239900² = 902266704020000, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21239900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21239903) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8555 + ... + 10754.

Almost surely, 2^21239900 is an apocalyptic number.

21239900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21239900 is an abundant number, since it is smaller than the sum of its proper divisors (29043340).

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

21239900 is a wasteful number, since it uses less digits than its factorization.

21239900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19334 (or 19327 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 21239900 is about 4608.6765996325. The cubic root of 21239900 is about 276.9390231004.

The spelling of 21239900 in words is "twenty-one million, two hundred thirty-nine thousand, nine hundred".