21015572 has 6 divisors (see below), whose sum is σ = 36777258. Its totient is φ = 10507784.

The previous prime is 21015571. The next prime is 21015581. The reversal of 21015572 is 27551012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 4726276 = 4036^2 + 2174^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2626943 + ... + 2626950.

It is an arithmetic number, because the mean of its divisors is an integer number (6129543).

Almost surely, 2^21015572 is an apocalyptic number.

It is an amenable number.

21015572 is a deficient number, since it is larger than the sum of its proper divisors (15761686).

21015572 is a wasteful number, since it uses less digits than its factorization.

21015572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5253897 (or 5253895 counting only the distinct ones).

The product of its (nonzero) digits is 700, while the sum is 23.

The square root of 21015572 is about 4584.2744245955. The cubic root of 21015572 is about 275.9605943882.

Adding to 21015572 its reverse (27551012), we get a palindrome (48566584).

The spelling of 21015572 in words is "twenty-one million, fifteen thousand, five hundred seventy-two".