121551561765 has 80 divisors (see below), whose sum is σ = 226298294640. Its totient is φ = 62366008320.

The previous prime is 121551561763. The next prime is 121551561779. The reversal of 121551561765 is 567165155121.

121551561765 is a `hidden beast` number, since 1 + 2 + 1 + 5 + 515 + 61 + 76 + 5 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 6585809409 + 114965752356 = 81153^2 + 339066^2 .

It is not a de Polignac number, because 121551561765 - 2¹ = 121551561763 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 121551561765.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121551561763) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1288095 + ... + 1379235.

It is an arithmetic number, because the mean of its divisors is an integer number (2828728683).

Almost surely, 2^121551561765 is an apocalyptic number.

121551561765 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

121551561765 is a deficient number, since it is larger than the sum of its proper divisors (104746732875).

121551561765 is an equidigital number, since it uses as much as digits as its factorization.

121551561765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91284 (or 91275 counting only the distinct ones).

The product of its digits is 315000, while the sum is 45.

The spelling of 121551561765 in words is "one hundred twenty-one billion, five hundred fifty-one million, five hundred sixty-one thousand, seven hundred sixty-five".