81157378370121 has 99 divisors (see below), whose sum is σ = 123106752567597. Its totient is φ = 53502180221880.

The previous prime is 81157378370099. The next prime is 81157378370149. The reversal of 81157378370121 is 12107387375118.

It is a happy number.

The square root of 81157378370121 is 9008739.

It is a perfect power (a square), and thus also a powerful number.

81157378370121 is a `hidden beast` number, since 8 + 1 + 15 + 73 + 78 + 370 + 121 = 666.

It is not a de Polignac number, because 81157378370121 - 2⁹ = 81157378369609 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81157378370221) by changing a digit.

It is a polite number, since it can be written in 98 ways as a sum of consecutive naturals, for example, 286775188446 + ... + 286775188728.

Almost surely, 2^{81157378370121} is an apocalyptic number.

81157378370121 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

81157378370121 is the 9008739-th square number.

81157378370121 is the 4504370-th centered octagonal number.

It is an amenable number.

81157378370121 is a deficient number, since it is larger than the sum of its proper divisors (41949374197476).

81157378370121 is an frugal number, since it uses more digits than its factorization.

81157378370121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 858 (or 417 counting only the distinct ones).

The product of its (nonzero) digits is 1975680, while the sum is 54.

The spelling of 81157378370121 in words is "eighty-one trillion, one hundred fifty-seven billion, three hundred seventy-eight million, three hundred seventy thousand, one hundred twenty-one".