81611918 has 8 divisors (see below), whose sum is σ = 122476512. Its totient is φ = 40786416.

The previous prime is 81611911. The next prime is 81611941. The reversal of 81611918 is 81911618.

It is a sphenic number, since it is the product of 3 distinct primes.

81611918 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81611911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3830 + ... + 13337.

It is an arithmetic number, because the mean of its divisors is an integer number (15309564).

Almost surely, 2^81611918 is an apocalyptic number.

81611918 is a deficient number, since it is larger than the sum of its proper divisors (40864594).

81611918 is a wasteful number, since it uses less digits than its factorization.

81611918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19546.

The product of its digits is 3456, while the sum is 35.

The square root of 81611918 is about 9033.9314808117. The cubic root of 81611918 is about 433.7616925261.

The spelling of 81611918 in words is "eighty-one million, six hundred eleven thousand, nine hundred eighteen".