81557773121 has 8 divisors (see below), whose sum is σ = 88977149184. Its totient is φ = 74139235920.

The previous prime is 81557773111. The next prime is 81557773169. The reversal of 81557773121 is 12137775518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81557773121 - 2¹⁴ = 81557756737 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81557773111) 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, 2960 + ... + 403886.

It is an arithmetic number, because the mean of its divisors is an integer number (11122143648).

Almost surely, 2^81557773121 is an apocalyptic number.

It is an amenable number.

81557773121 is a deficient number, since it is larger than the sum of its proper divisors (7419376063).

81557773121 is a wasteful number, since it uses less digits than its factorization.

81557773121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 419431.

The product of its digits is 411600, while the sum is 47.

The spelling of 81557773121 in words is "eighty-one billion, five hundred fifty-seven million, seven hundred seventy-three thousand, one hundred twenty-one".