21707172 has 18 divisors (see below), whose sum is σ = 54870998. Its totient is φ = 7235712.

The previous prime is 21707171. The next prime is 21707173. The reversal of 21707172 is 27170712.

It is an interprime number because it is at equal distance from previous prime (21707171) and next prime (21707173).

It can be written as a sum of positive squares in only one way, i.e., 20738916 + 968256 = 4554^2 + 984^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is not an unprimeable number, because it can be changed into a prime (21707171) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 301453 + ... + 301524.

Almost surely, 2^21707172 is an apocalyptic number.

It is an amenable number.

21707172 is an abundant number, since it is smaller than the sum of its proper divisors (33163826).

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

21707172 is a wasteful number, since it uses less digits than its factorization.

21707172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 602987 (or 602982 counting only the distinct ones).

The product of its (nonzero) digits is 1372, while the sum is 27.

The square root of 21707172 is about 4659.0956203967. The cubic root of 21707172 is about 278.9551706598.

Adding to 21707172 its reverse (27170712), we get a palindrome (48877884).

It can be divided in two parts, 2170717 and 2, that multiplied together give a palindrome (4341434).

The spelling of 21707172 in words is "twenty-one million, seven hundred seven thousand, one hundred seventy-two".