640312601661 has 8 divisors (see below), whose sum is σ = 948611261760. Its totient is φ = 426875067756.

The previous prime is 640312601657. The next prime is 640312601681. The reversal of 640312601661 is 166106213046.

It is a happy number.

640312601661 is a `hidden beast` number, since 6 + 40 + 3 + 1 + 2 + 601 + 6 + 6 + 1 = 666.

It is not a de Polignac number, because 640312601661 - 2² = 640312601657 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640312601611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11857640745 + ... + 11857640798.

It is an arithmetic number, because the mean of its divisors is an integer number (118576407720).

Almost surely, 2^640312601661 is an apocalyptic number.

It is an amenable number.

640312601661 is a deficient number, since it is larger than the sum of its proper divisors (308298660099).

640312601661 is a wasteful number, since it uses less digits than its factorization.

640312601661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23715281552 (or 23715281546 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The spelling of 640312601661 in words is "six hundred forty billion, three hundred twelve million, six hundred one thousand, six hundred sixty-one".