661699615647 has 16 divisors (see below), whose sum is σ = 1011484956672. Its totient is φ = 376921273440.

The previous prime is 661699615637. The next prime is 661699615649. The reversal of 661699615647 is 746516996166.

It is not a de Polignac number, because 661699615647 - 2⁸ = 661699615391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661699615649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49692879 + ... + 49706192.

It is an arithmetic number, because the mean of its divisors is an integer number (63217809792).

Almost surely, 2^661699615647 is an apocalyptic number.

661699615647 is a deficient number, since it is larger than the sum of its proper divisors (349785341025).

661699615647 is a wasteful number, since it uses less digits than its factorization.

661699615647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99399398.

The product of its digits is 88179840, while the sum is 66.

The spelling of 661699615647 in words is "six hundred sixty-one billion, six hundred ninety-nine million, six hundred fifteen thousand, six hundred forty-seven".