21688710 has 32 divisors (see below), whose sum is σ = 52565760. Its totient is φ = 5726688.

The previous prime is 21688703. The next prime is 21688721. The reversal of 21688710 is 1788612.

It is a happy number.

It is a congruent number.

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, 420 + ... + 6599.

It is an arithmetic number, because the mean of its divisors is an integer number (1642680).

Almost surely, 2^21688710 is an apocalyptic number.

21688710 is an abundant number, since it is smaller than the sum of its proper divisors (30877050).

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

21688710 is a wasteful number, since it uses less digits than its factorization.

21688710 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7132.

The product of its (nonzero) digits is 5376, while the sum is 33.

The square root of 21688710 is about 4657.1139131441. The cubic root of 21688710 is about 278.8760642229.

It can be divided in two parts, 2168 and 8710, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 21688710 in words is "twenty-one million, six hundred eighty-eight thousand, seven hundred ten".