21700872 has 84 divisors (see below), whose sum is σ = 62022285. Its totient is φ = 7115040.

The previous prime is 21700843. The next prime is 21700873. The reversal of 21700872 is 27800712.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 14699556 + 7001316 = 3834^2 + 2646^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3294.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21700873) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 355722 + ... + 355782.

Almost surely, 2^21700872 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21700872

21700872 is an abundant number, since it is smaller than the sum of its proper divisors (40321413).

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

21700872 is an frugal number, since it uses more digits than its factorization.

21700872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146 (or 66 counting only the distinct ones).

The product of its (nonzero) digits is 1568, while the sum is 27.

The square root of 21700872 is about 4658.4194744570. The cubic root of 21700872 is about 278.9281813063.

Multiplying 21700872 by its product of nonzero digits (1568), we get a square (34026967296 = 184464²).

The spelling of 21700872 in words is "twenty-one million, seven hundred thousand, eight hundred seventy-two".