21577972 has 48 divisors (see below), whose sum is σ = 43218000. Its totient is φ = 9354240.

The previous prime is 21577951. The next prime is 21577973. The reversal of 21577972 is 27977512.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 2446096 + 19131876 = 1564^2 + 4374^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21577973) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 61654 + ... + 62002.

It is an arithmetic number, because the mean of its divisors is an integer number (900375).

Almost surely, 2^21577972 is an apocalyptic number.

It is an amenable number.

21577972 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

21577972 is a wasteful number, since it uses less digits than its factorization.

21577972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 436 (or 434 counting only the distinct ones).

The product of its digits is 61740, while the sum is 40.

The square root of 21577972 is about 4645.2095754659. The cubic root of 21577972 is about 278.4006265950.

It can be divided in two parts, 215 and 77972, that added together give a palindrome (78187).

The spelling of 21577972 in words is "twenty-one million, five hundred seventy-seven thousand, nine hundred seventy-two".