81387760 has 20 divisors (see below), whose sum is σ = 189226728. Its totient is φ = 32555072.

The previous prime is 81387751. The next prime is 81387769. The reversal of 81387760 is 6778318.

It is an interprime number because it is at equal distance from previous prime (81387751) and next prime (81387769).

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81387769) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 508594 + ... + 508753.

Almost surely, 2^81387760 is an apocalyptic number.

81387760 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81387760 is an abundant number, since it is smaller than the sum of its proper divisors (107838968).

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

81387760 is a wasteful number, since it uses less digits than its factorization.

81387760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1017360 (or 1017354 counting only the distinct ones).

The product of its (nonzero) digits is 56448, while the sum is 40.

The square root of 81387760 is about 9021.5165022295. The cubic root of 81387760 is about 433.3642002996.

The spelling of 81387760 in words is "eighty-one million, three hundred eighty-seven thousand, seven hundred sixty".