21172770 has 48 divisors (see below), whose sum is σ = 56339712. Its totient is φ = 5513760.

The previous prime is 21172763. The next prime is 21172787. The reversal of 21172770 is 7727112.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1135 + ... + 6605.

It is an arithmetic number, because the mean of its divisors is an integer number (1173744).

Almost surely, 2^21172770 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21172770, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28169856).

21172770 is an abundant number, since it is smaller than the sum of its proper divisors (35166942).

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

21172770 is a wasteful number, since it uses less digits than its factorization.

21172770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5527 (or 5524 counting only the distinct ones).

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

The square root of 21172770 is about 4601.3878341214. The cubic root of 21172770 is about 276.6469542898.

Adding to 21172770 its reverse (7727112), we get a palindrome (28899882).

The spelling of 21172770 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred seventy".