81778445525 has 24 divisors (see below), whose sum is σ = 116155839360. Its totient is φ = 55948858560.

The previous prime is 81778445521. The next prime is 81778445531. The reversal of 81778445525 is 52554487718.

It is a happy number.

It is not a de Polignac number, because 81778445525 - 2² = 81778445521 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81778445521) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 455414 + ... + 609063.

It is an arithmetic number, because the mean of its divisors is an integer number (4839826640).

Almost surely, 2^81778445525 is an apocalyptic number.

It is an amenable number.

81778445525 is a deficient number, since it is larger than the sum of its proper divisors (34377393835).

81778445525 is a wasteful number, since it uses less digits than its factorization.

81778445525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1064933 (or 1064928 counting only the distinct ones).

The product of its digits is 12544000, while the sum is 56.

The spelling of 81778445525 in words is "eighty-one billion, seven hundred seventy-eight million, four hundred forty-five thousand, five hundred twenty-five".