81560018 has 4 divisors (see below), whose sum is σ = 122340030. Its totient is φ = 40780008.

The previous prime is 81560009. The next prime is 81560023. The reversal of 81560018 is 81006518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 79691329 + 1868689 = 8927^2 + 1367^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20390003 + ... + 20390006.

Almost surely, 2^81560018 is an apocalyptic number.

81560018 is a deficient number, since it is larger than the sum of its proper divisors (40780012).

81560018 is a wasteful number, since it uses less digits than its factorization.

81560018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40780011.

The product of its (nonzero) digits is 1920, while the sum is 29.

The square root of 81560018 is about 9031.0585204615. The cubic root of 81560018 is about 433.6697247262.

The spelling of 81560018 in words is "eighty-one million, five hundred sixty thousand, eighteen".