64155861661 has 4 divisors (see below), whose sum is σ = 64169969500. Its totient is φ = 64141753824.

The previous prime is 64155861631. The next prime is 64155861691. The reversal of 64155861661 is 16616855146.

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

It is an interprime number because it is at equal distance from previous prime (64155861631) and next prime (64155861691).

It can be written as a sum of positive squares in 2 ways, for example, as 53042696100 + 11113165561 = 230310^2 + 105419^2 .

It is a cyclic number.

It is not a de Polignac number, because 64155861661 - 2¹⁹ = 64155337373 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64155861611) 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, 7047096 + ... + 7056193.

It is an arithmetic number, because the mean of its divisors is an integer number (16042492375).

Almost surely, 2^64155861661 is an apocalyptic number.

It is an amenable number.

64155861661 is a deficient number, since it is larger than the sum of its proper divisors (14107839).

64155861661 is a wasteful number, since it uses less digits than its factorization.

64155861661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14107838.

The product of its digits is 1036800, while the sum is 49.

The spelling of 64155861661 in words is "sixty-four billion, one hundred fifty-five million, eight hundred sixty-one thousand, six hundred sixty-one".