21129636 has 24 divisors (see below), whose sum is σ = 53784864. Its totient is φ = 6402880.

The previous prime is 21129613. The next prime is 21129643. The reversal of 21129636 is 63692112.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79905 + ... + 80168.

It is an arithmetic number, because the mean of its divisors is an integer number (2241036).

Almost surely, 2^21129636 is an apocalyptic number.

It is an amenable number.

21129636 is an abundant number, since it is smaller than the sum of its proper divisors (32655228).

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

21129636 is a wasteful number, since it uses less digits than its factorization.

21129636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160091 (or 160089 counting only the distinct ones).

The product of its digits is 3888, while the sum is 30.

The square root of 21129636 is about 4596.6983803595. The cubic root of 21129636 is about 276.4589612167.

The spelling of 21129636 in words is "twenty-one million, one hundred twenty-nine thousand, six hundred thirty-six".