81121975 has 12 divisors (see below), whose sum is σ = 109736280. Its totient is φ = 58997600.

The previous prime is 81121967. The next prime is 81121981. The reversal of 81121975 is 57912118.

81121975 = T₃₈₃₅ + T₃₈₃₆ + ... + T₃₈₄₅.

It is a happy number.

It is not a de Polignac number, because 81121975 - 2³ = 81121967 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81121975.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 147220 + ... + 147769.

It is an arithmetic number, because the mean of its divisors is an integer number (9144690).

Almost surely, 2^81121975 is an apocalyptic number.

81121975 is a deficient number, since it is larger than the sum of its proper divisors (28614305).

81121975 is a wasteful number, since it uses less digits than its factorization.

81121975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 295010 (or 295005 counting only the distinct ones).

The product of its digits is 5040, while the sum is 34.

The square root of 81121975 is about 9006.7738397275. The cubic root of 81121975 is about 432.8919453664.

The spelling of 81121975 in words is "eighty-one million, one hundred twenty-one thousand, nine hundred seventy-five".