81218171658 has 16 divisors (see below), whose sum is σ = 174931446816. Its totient is φ = 24990206640.

The previous prime is 81218171611. The next prime is 81218171659. The reversal of 81218171658 is 85617181218.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (81218171659) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 520629228 + ... + 520629383.

It is an arithmetic number, because the mean of its divisors is an integer number (10933215426).

Almost surely, 2^81218171658 is an apocalyptic number.

81218171658 is an abundant number, since it is smaller than the sum of its proper divisors (93713275158).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81218171658 is a wasteful number, since it uses less digits than its factorization.

81218171658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1041258629.

The product of its digits is 215040, while the sum is 48.

The spelling of 81218171658 in words is "eighty-one billion, two hundred eighteen million, one hundred seventy-one thousand, six hundred fifty-eight".