81137750121 has 6 divisors (see below), whose sum is σ = 117198972410. Its totient is φ = 54091833408.

The previous prime is 81137750053. The next prime is 81137750143. The reversal of 81137750121 is 12105773118.

81137750121 is a `hidden beast` number, since 81 + 1 + 3 + 77 + 501 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 62505500121 + 18632250000 = 250011^2 + 136500^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81137750121 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81137750171) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4507652776 + ... + 4507652793.

Almost surely, 2^81137750121 is an apocalyptic number.

It is an amenable number.

81137750121 is a deficient number, since it is larger than the sum of its proper divisors (36061222289).

81137750121 is a wasteful number, since it uses less digits than its factorization.

81137750121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9015305575 (or 9015305572 counting only the distinct ones).

The product of its (nonzero) digits is 11760, while the sum is 36.

The spelling of 81137750121 in words is "eighty-one billion, one hundred thirty-seven million, seven hundred fifty thousand, one hundred twenty-one".