661523663771 has 4 divisors (see below), whose sum is σ = 670840898544. Its totient is φ = 652206429000.

The previous prime is 661523663767. The next prime is 661523663789. The reversal of 661523663771 is 177366325166.

It is a happy number.

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 661523663771 - 2² = 661523663767 is a prime.

It is a super-2 number, since 2×661523663771² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661523663761) 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, 4658617280 + ... + 4658617421.

It is an arithmetic number, because the mean of its divisors is an integer number (167710224636).

Almost surely, 2^661523663771 is an apocalyptic number.

661523663771 is a deficient number, since it is larger than the sum of its proper divisors (9317234773).

661523663771 is an equidigital number, since it uses as much as digits as its factorization.

661523663771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9317234772.

The product of its digits is 5715360, while the sum is 53.

The spelling of 661523663771 in words is "six hundred sixty-one billion, five hundred twenty-three million, six hundred sixty-three thousand, seven hundred seventy-one".