51661505655 has 12 divisors (see below), whose sum is σ = 89546609880. Its totient is φ = 27552802992.

The previous prime is 51661505639. The next prime is 51661505659. The reversal of 51661505655 is 55650516615.

It is not a de Polignac number, because 51661505655 - 2⁴ = 51661505639 is a prime.

It is a super-2 number, since 2×51661505655² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 1148033459 = 51661505655 / (5 + 1 + 6 + 6 + 1 + 5 + 0 + 5 + 6 + 5 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 51661505655.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51661505659) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 574016685 + ... + 574016774.

It is an arithmetic number, because the mean of its divisors is an integer number (7462217490).

Almost surely, 2^51661505655 is an apocalyptic number.

51661505655 is a deficient number, since it is larger than the sum of its proper divisors (37885104225).

51661505655 is a wasteful number, since it uses less digits than its factorization.

51661505655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148033470 (or 1148033467 counting only the distinct ones).

The product of its (nonzero) digits is 675000, while the sum is 45.

The spelling of 51661505655 in words is "fifty-one billion, six hundred sixty-one million, five hundred five thousand, six hundred fifty-five".