21129612 has 24 divisors (see below), whose sum is σ = 56345856. Its totient is φ = 6037008.

The previous prime is 21129587. The next prime is 21129613. The reversal of 21129612 is 21692112.

It is not an unprimeable number, because it can be changed into a prime (21129613) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 125688 + ... + 125855.

It is an arithmetic number, because the mean of its divisors is an integer number (2347744).

Almost surely, 2^21129612 is an apocalyptic number.

It is an amenable number.

21129612 is an abundant number, since it is smaller than the sum of its proper divisors (35216244).

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

21129612 is a wasteful number, since it uses less digits than its factorization.

21129612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251557 (or 251555 counting only the distinct ones).

The product of its digits is 432, while the sum is 24.

The square root of 21129612 is about 4596.6957697894. The cubic root of 21129612 is about 276.4588565451.

Subtracting 21129612 from its reverse (21692112), we obtain a square (562500 = 750²).

The spelling of 21129612 in words is "twenty-one million, one hundred twenty-nine thousand, six hundred twelve".