21187668 has 12 divisors (see below), whose sum is σ = 49437920. Its totient is φ = 7062552.

The previous prime is 21187633. The next prime is 21187687. The reversal of 21187668 is 86678112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 882808 + ... + 882831.

Almost surely, 2^21187668 is an apocalyptic number.

It is an amenable number.

21187668 is an abundant number, since it is smaller than the sum of its proper divisors (28250252).

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

21187668 is a wasteful number, since it uses less digits than its factorization.

21187668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1765646 (or 1765644 counting only the distinct ones).

The product of its digits is 32256, while the sum is 39.

The square root of 21187668 is about 4603.0064088593. The cubic root of 21187668 is about 276.7118256635.

It can be divided in two parts, 21 and 187668, that multiplied together give a triangular number (3941028 = T₂₈₀₇).

The spelling of 21187668 in words is "twenty-one million, one hundred eighty-seven thousand, six hundred sixty-eight".