21566864650 has 12 divisors (see below), whose sum is σ = 40114368342. Its totient is φ = 8626745840.

The previous prime is 21566864593. The next prime is 21566864659. The reversal of 21566864650 is 5646866512.

It can be written as a sum of positive squares in 3 ways, for example, as 16828056729 + 4738807921 = 129723^2 + 68839^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21566864594 and 21566864603.

It is not an unprimeable number, because it can be changed into a prime (21566864659) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 215668597 + ... + 215668696.

Almost surely, 2^21566864650 is an apocalyptic number.

21566864650 is a deficient number, since it is larger than the sum of its proper divisors (18547503692).

21566864650 is a wasteful number, since it uses less digits than its factorization.

21566864650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 431337305 (or 431337300 counting only the distinct ones).

The product of its (nonzero) digits is 2073600, while the sum is 49.

The spelling of 21566864650 in words is "twenty-one billion, five hundred sixty-six million, eight hundred sixty-four thousand, six hundred fifty".