21261624536666 has 4 divisors (see below), whose sum is σ = 31892436805002. Its totient is φ = 10630812268332.

The previous prime is 21261624536623. The next prime is 21261624536681. The reversal of 21261624536666 is 66663542616212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20566270350025 + 695354186641 = 4535005^2 + 833879^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5315406134165 + ... + 5315406134168.

Almost surely, 2^{21261624536666} is an apocalyptic number.

21261624536666 is a deficient number, since it is larger than the sum of its proper divisors (10630812268336).

21261624536666 is a wasteful number, since it uses less digits than its factorization.

21261624536666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10630812268335.

The product of its digits is 22394880, while the sum is 56.

The spelling of 21261624536666 in words is "twenty-one trillion, two hundred sixty-one billion, six hundred twenty-four million, five hundred thirty-six thousand, six hundred sixty-six".