661645244642 has 4 divisors (see below), whose sum is σ = 992467866966. Its totient is φ = 330822622320.

The previous prime is 661645244641. The next prime is 661645244647. The reversal of 661645244642 is 246442546166.

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., 647331275761 + 14313968881 = 804569^2 + 119641^2 .

It is not an unprimeable number, because it can be changed into a prime (661645244641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165411311159 + ... + 165411311162.

Almost surely, 2^661645244642 is an apocalyptic number.

661645244642 is a deficient number, since it is larger than the sum of its proper divisors (330822622324).

661645244642 is a wasteful number, since it uses less digits than its factorization.

661645244642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330822622323.

The product of its digits is 6635520, while the sum is 50.

The spelling of 661645244642 in words is "six hundred sixty-one billion, six hundred forty-five million, two hundred forty-four thousand, six hundred forty-two".