21688716 has 48 divisors (see below), whose sum is σ = 59709440. Its totient is φ = 5996160.

The previous prime is 21688703. The next prime is 21688721. The reversal of 21688716 is 61788612.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1561 + ... + 6768.

Almost surely, 2^21688716 is an apocalyptic number.

It is an amenable number.

21688716 is an abundant number, since it is smaller than the sum of its proper divisors (38020724).

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

21688716 is a wasteful number, since it uses less digits than its factorization.

21688716 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8374 (or 8372 counting only the distinct ones).

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

The square root of 21688716 is about 4657.1145573198. The cubic root of 21688716 is about 278.8760899391.

The spelling of 21688716 in words is "twenty-one million, six hundred eighty-eight thousand, seven hundred sixteen".