81597780 has 240 divisors, whose sum is σ = 295162560. Its totient is φ = 18662400.

The previous prime is 81597743. The next prime is 81597811. The reversal of 81597780 is 8779518.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 338460 + ... + 338700.

It is an arithmetic number, because the mean of its divisors is an integer number (1229844).

Almost surely, 2^81597780 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 81597780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147581280).

81597780 is an abundant number, since it is smaller than the sum of its proper divisors (213564780).

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

81597780 is a wasteful number, since it uses less digits than its factorization.

81597780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 292 (or 281 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 45.

The square root of 81597780 is about 9033.1489526078. The cubic root of 81597780 is about 433.7366435827.

The spelling of 81597780 in words is "eighty-one million, five hundred ninety-seven thousand, seven hundred eighty".