21711680 has 56 divisors (see below), whose sum is σ = 54437280. Its totient is φ = 8225280.

The previous prime is 21711619. The next prime is 21711709. The reversal of 21711680 is 8611712.

It is a congruent number.

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, 4295 + ... + 7865.

Almost surely, 2^21711680 is an apocalyptic number.

21711680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21711680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27218640).

21711680 is an abundant number, since it is smaller than the sum of its proper divisors (32725600).

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

21711680 is a wasteful number, since it uses less digits than its factorization.

21711680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3607 (or 3597 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 21711680 is about 4659.5793801587. The cubic root of 21711680 is about 278.9744798367.

The spelling of 21711680 in words is "twenty-one million, seven hundred eleven thousand, six hundred eighty".