661855262599 has 4 divisors (see below), whose sum is σ = 665681015736. Its totient is φ = 658029509464.

The previous prime is 661855262581. The next prime is 661855262611. The reversal of 661855262599 is 995262558166.

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

It is a cyclic number.

It is not a de Polignac number, because 661855262599 - 2⁵ = 661855262567 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 661855262599.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661855262539) 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, 1912876309 + ... + 1912876654.

It is an arithmetic number, because the mean of its divisors is an integer number (166420253934).

Almost surely, 2^661855262599 is an apocalyptic number.

661855262599 is a deficient number, since it is larger than the sum of its proper divisors (3825753137).

661855262599 is a wasteful number, since it uses less digits than its factorization.

661855262599 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3825753136.

The product of its digits is 69984000, while the sum is 64.

The spelling of 661855262599 in words is "six hundred sixty-one billion, eight hundred fifty-five million, two hundred sixty-two thousand, five hundred ninety-nine".