81583925641 has 3 divisors (see below), whose sum is σ = 81584211271. Its totient is φ = 81583640012.

The previous prime is 81583925639. The next prime is 81583925651. The reversal of 81583925641 is 14652938518.

It is a happy number.

The square root of 81583925641 is 285629.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 68345122041 + 13238803600 = 261429^2 + 115060^2 .

It is not a de Polignac number, because 81583925641 - 2¹ = 81583925639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81583925611) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 142815 + ... + 428443.

Almost surely, 2^81583925641 is an apocalyptic number.

81583925641 is the 285629-th square number.

81583925641 is the 142815-th centered octagonal number.

It is an amenable number.

81583925641 is a deficient number, since it is larger than the sum of its proper divisors (285630).

81583925641 is an frugal number, since it uses more digits than its factorization.

81583925641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571258 (or 285629 counting only the distinct ones).

The product of its digits is 2073600, while the sum is 52.

The spelling of 81583925641 in words is "eighty-one billion, five hundred eighty-three million, nine hundred twenty-five thousand, six hundred forty-one".