81218423225 has 12 divisors (see below), whose sum is σ = 100721835756. Its totient is φ = 64967647680.

The previous prime is 81218423159. The next prime is 81218423227. The reversal of 81218423225 is 52232481218.

It can be written as a sum of positive squares in 6 ways, for example, as 750321664 + 80468101561 = 27392^2 + 283669^2 .

It is not a de Polignac number, because 81218423225 - 2¹² = 81218419129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81218423227) 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, 62759 + ... + 407891.

It is an arithmetic number, because the mean of its divisors is an integer number (8393486313).

Almost surely, 2^81218423225 is an apocalyptic number.

It is an amenable number.

81218423225 is a deficient number, since it is larger than the sum of its proper divisors (19503412531).

81218423225 is a wasteful number, since it uses less digits than its factorization.

81218423225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354556 (or 354551 counting only the distinct ones).

The product of its digits is 61440, while the sum is 38.

The spelling of 81218423225 in words is "eighty-one billion, two hundred eighteen million, four hundred twenty-three thousand, two hundred twenty-five".