21099872 has 12 divisors (see below), whose sum is σ = 41540436. Its totient is φ = 10549920.

The previous prime is 21099863. The next prime is 21099887. The reversal of 21099872 is 27899012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 329654 + ... + 329717.

It is an arithmetic number, because the mean of its divisors is an integer number (3461703).

Almost surely, 2^21099872 is an apocalyptic number.

It is an amenable number.

21099872 is a deficient number, since it is larger than the sum of its proper divisors (20440564).

21099872 is an equidigital number, since it uses as much as digits as its factorization.

21099872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 659381 (or 659373 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 21099872 is about 4593.4596983102. The cubic root of 21099872 is about 276.3290900535.

The spelling of 21099872 in words is "twenty-one million, ninety-nine thousand, eight hundred seventy-two".