81977760 has 72 divisors (see below), whose sum is σ = 279754020. Its totient is φ = 21860352.

The previous prime is 81977743. The next prime is 81977767. The reversal of 81977760 is 6777918.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 68757264 + 13220496 = 8292^2 + 3636^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is not an unprimeable number, because it can be changed into a prime (81977767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27025 + ... + 29904.

Almost surely, 2^81977760 is an apocalyptic number.

81977760 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81977760 is an abundant number, since it is smaller than the sum of its proper divisors (197776260).

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

81977760 is a wasteful number, since it uses less digits than its factorization.

81977760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56950 (or 56939 counting only the distinct ones).

The product of its (nonzero) digits is 148176, while the sum is 45.

The square root of 81977760 is about 9054.1570562919. The cubic root of 81977760 is about 434.4088680871.

The spelling of 81977760 in words is "eighty-one million, nine hundred seventy-seven thousand, seven hundred sixty".