81907224168121 has 27 divisors (see below), whose sum is σ = 90275926855023. Its totient is φ = 74258477536320.

The previous prime is 81907224168101. The next prime is 81907224168139. The reversal of 81907224168121 is 12186142270918.

It is a happy number.

The square root of 81907224168121 is 9050261.

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

It can be written as a sum of positive squares in only one way, i.e., 41507674596025 + 40399549572096 = 6442645^2 + 6356064^2 .

It is not a de Polignac number, because 81907224168121 - 2²³ = 81907215779513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81907224168101) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 46092978385 + ... + 46092980161.

Almost surely, 2^{81907224168121} is an apocalyptic number.

81907224168121 is the 9050261-st square number.

81907224168121 is the 4525131-st centered octagonal number.

It is an amenable number.

81907224168121 is a deficient number, since it is larger than the sum of its proper divisors (8368702686902).

81907224168121 is an frugal number, since it uses more digits than its factorization.

81907224168121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4502 (or 2251 counting only the distinct ones).

The product of its (nonzero) digits is 774144, while the sum is 52.

The spelling of 81907224168121 in words is "eighty-one trillion, nine hundred seven billion, two hundred twenty-four million, one hundred sixty-eight thousand, one hundred twenty-one".