81618456625 has 8 divisors (see below), whose sum is σ = 101859834024. Its totient is φ = 65294765200.

The previous prime is 81618456613. The next prime is 81618456637. The reversal of 81618456625 is 52665481618.

It is an interprime number because it is at equal distance from previous prime (81618456613) and next prime (81618456637).

It can be written as a sum of positive squares in 4 ways, for example, as 468679201 + 81149777424 = 21649^2 + 284868^2 .

It is not a de Polignac number, because 81618456625 - 2¹³ = 81618448433 is a prime.

It is a hoax number, since the sum of its digits (52) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 326473702 + ... + 326473951.

It is an arithmetic number, because the mean of its divisors is an integer number (12732479253).

Almost surely, 2^81618456625 is an apocalyptic number.

It is an amenable number.

81618456625 is a deficient number, since it is larger than the sum of its proper divisors (20241377399).

81618456625 is an equidigital number, since it uses as much as digits as its factorization.

81618456625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 652947668 (or 652947658 counting only the distinct ones).

The product of its digits is 2764800, while the sum is 52.

The spelling of 81618456625 in words is "eighty-one billion, six hundred eighteen million, four hundred fifty-six thousand, six hundred twenty-five".