21137572 has 6 divisors (see below), whose sum is σ = 36990758. Its totient is φ = 10568784.

The previous prime is 21137563. The next prime is 21137609. The reversal of 21137572 is 27573112.

It can be written as a sum of positive squares in only one way, i.e., 16048036 + 5089536 = 4006^2 + 2256^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21137572.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2642193 + ... + 2642200.

Almost surely, 2^21137572 is an apocalyptic number.

21137572 is the 2458-th centered heptagonal number.

It is an amenable number.

21137572 is a deficient number, since it is larger than the sum of its proper divisors (15853186).

21137572 is a wasteful number, since it uses less digits than its factorization.

21137572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5284397 (or 5284395 counting only the distinct ones).

The product of its digits is 2940, while the sum is 28.

The square root of 21137572 is about 4597.5615275926. The cubic root of 21137572 is about 276.4935682760.

The spelling of 21137572 in words is "twenty-one million, one hundred thirty-seven thousand, five hundred seventy-two".