81285121 has 2 divisors, whose sum is σ = 81285122. Its totient is φ = 81285120.

The previous prime is 81285101. The next prime is 81285157. The reversal of 81285121 is 12158218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 79566400 + 1718721 = 8920^2 + 1311^2 .

It is a cyclic number.

It is not a de Polignac number, because 81285121 - 2⁵ = 81285089 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81285121.

It is not a weakly prime, because it can be changed into another prime (81285101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40642560 + 40642561.

It is an arithmetic number, because the mean of its divisors is an integer number (40642561).

Almost surely, 2^81285121 is an apocalyptic number.

It is an amenable number.

81285121 is a deficient number, since it is larger than the sum of its proper divisors (1).

81285121 is an equidigital number, since it uses as much as digits as its factorization.

81285121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1280, while the sum is 28.

The square root of 81285121 is about 9015.8261407372. The cubic root of 81285121 is about 433.1819502112.

It can be divided in two parts, 81285 and 121, that added together give a triangular number (81406 = T₄₀₃).

The spelling of 81285121 in words is "eighty-one million, two hundred eighty-five thousand, one hundred twenty-one".