661904775715 has 4 divisors (see below), whose sum is σ = 794285730864. Its totient is φ = 529523820568.

The previous prime is 661904775713. The next prime is 661904775769. The reversal of 661904775715 is 517577409166.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 517577409166 = 2 ⋅258788704583.

It is a cyclic number.

It is not a de Polignac number, because 661904775715 - 2¹ = 661904775713 is a prime.

It is a super-2 number, since 2×661904775715² (a number of 24 digits) contains 22 as substring.

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 661904775715.

It is not an unprimeable number, because it can be changed into a prime (661904775713) 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, 66190477567 + ... + 66190477576.

It is an arithmetic number, because the mean of its divisors is an integer number (198571432716).

Almost surely, 2^661904775715 is an apocalyptic number.

661904775715 is a deficient number, since it is larger than the sum of its proper divisors (132380955149).

661904775715 is a wasteful number, since it uses less digits than its factorization.

661904775715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132380955148.

The product of its (nonzero) digits is 11113200, while the sum is 58.

The spelling of 661904775715 in words is "six hundred sixty-one billion, nine hundred four million, seven hundred seventy-five thousand, seven hundred fifteen".