81523767780 has 576 divisors, whose sum is σ = 328239475200. Its totient is φ = 15895388160.

The previous prime is 81523767779. The next prime is 81523767781. The reversal of 81523767780 is 8776732518.

81523767780 is a `hidden beast` number, since 81 + 52 + 376 + 77 + 80 = 666.

It is an interprime number because it is at equal distance from previous prime (81523767779) and next prime (81523767781).

It is a super-2 number, since 2×81523767780² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81523767781) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 12756826 + ... + 12763214.

It is an arithmetic number, because the mean of its divisors is an integer number (569860200).

Almost surely, 2^81523767780 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81523767780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (164119737600).

81523767780 is an abundant number, since it is smaller than the sum of its proper divisors (246715707420).

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

81523767780 is a wasteful number, since it uses less digits than its factorization.

81523767780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6484 (or 6479 counting only the distinct ones).

The product of its (nonzero) digits is 3951360, while the sum is 54.

The spelling of 81523767780 in words is "eighty-one billion, five hundred twenty-three million, seven hundred sixty-seven thousand, seven hundred eighty".