81945775 has 12 divisors (see below), whose sum is σ = 102205512. Its totient is φ = 65174240.

The previous prime is 81945767. The next prime is 81945779. The reversal of 81945775 is 57754918.

It is a happy number.

It is not a de Polignac number, because 81945775 - 2³ = 81945767 is a prime.

It is a super-2 number, since 2×81945775² = 13430220080701250, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81945779) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5149 + ... + 13798.

It is an arithmetic number, because the mean of its divisors is an integer number (8517126).

Almost surely, 2^81945775 is an apocalyptic number.

81945775 is a deficient number, since it is larger than the sum of its proper divisors (20259737).

81945775 is a wasteful number, since it uses less digits than its factorization.

81945775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19130 (or 19125 counting only the distinct ones).

The product of its digits is 352800, while the sum is 46.

The square root of 81945775 is about 9052.3905682422. The cubic root of 81945775 is about 434.3523634323.

The spelling of 81945775 in words is "eighty-one million, nine hundred forty-five thousand, seven hundred seventy-five".