21661264610 has 8 divisors (see below), whose sum is σ = 38990276316. Its totient is φ = 8664505840.

The previous prime is 21661264589. The next prime is 21661264613. The reversal of 21661264610 is 1646216612.

It can be written as a sum of positive squares in 2 ways, for example, as 20643080329 + 1018184281 = 143677^2 + 31909^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21661264613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1083063221 + ... + 1083063240.

Almost surely, 2^21661264610 is an apocalyptic number.

21661264610 is a deficient number, since it is larger than the sum of its proper divisors (17329011706).

21661264610 is a wasteful number, since it uses less digits than its factorization.

21661264610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2166126468.

The product of its (nonzero) digits is 20736, while the sum is 35.

The spelling of 21661264610 in words is "twenty-one billion, six hundred sixty-one million, two hundred sixty-four thousand, six hundred ten".