21706872 has 32 divisors (see below), whose sum is σ = 59201280. Its totient is φ = 6577760.

The previous prime is 21706837. The next prime is 21706889. The reversal of 21706872 is 27860712.

It is a Harshad number since it is a multiple of its sum of digits (33).

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, 40848 + ... + 41375.

It is an arithmetic number, because the mean of its divisors is an integer number (1850040).

Almost surely, 2^21706872 is an apocalyptic number.

21706872 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21706872 is an abundant number, since it is smaller than the sum of its proper divisors (37494408).

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

21706872 is a wasteful number, since it uses less digits than its factorization.

21706872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82243 (or 82239 counting only the distinct ones).

The product of its (nonzero) digits is 9408, while the sum is 33.

The square root of 21706872 is about 4659.0634251961. The cubic root of 21706872 is about 278.9538855709.

It can be divided in two parts, 21706 and 872, that added together give a triangular number (22578 = T₂₁₂).

The spelling of 21706872 in words is "twenty-one million, seven hundred six thousand, eight hundred seventy-two".