21562866649 has 3 divisors (see below), whose sum is σ = 21563013493. Its totient is φ = 21562719806.

The previous prime is 21562866599. The next prime is 21562866667. The reversal of 21562866649 is 94666826512.

The square root of 21562866649 is 146843.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a de Polignac number, because none of the positive numbers 2^k-21562866649 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21562866649.

It is not an unprimeable number, because it can be changed into a prime (21562866749) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 73422 + ... + 220264.

Almost surely, 2^21562866649 is an apocalyptic number.

21562866649 is the 146843-rd square number.

21562866649 is the 73422-nd centered octagonal number.

It is an amenable number.

21562866649 is a deficient number, since it is larger than the sum of its proper divisors (146844).

21562866649 is an frugal number, since it uses more digits than its factorization.

21562866649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293686 (or 146843 counting only the distinct ones).

The product of its digits is 7464960, while the sum is 55.

The spelling of 21562866649 in words is "twenty-one billion, five hundred sixty-two million, eight hundred sixty-six thousand, six hundred forty-nine".