81776640 has 208 divisors, whose sum is σ = 287798976. Its totient is φ = 19824640.

The previous prime is 81776621. The next prime is 81776641. The reversal of 81776640 is 4667718.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81776641) 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 15 ways as a sum of consecutive naturals, for example, 7434235 + ... + 7434245.

Almost surely, 2^81776640 is an apocalyptic number.

81776640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81776640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (143899488).

81776640 is an abundant number, since it is smaller than the sum of its proper divisors (206022336).

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

81776640 is an equidigital number, since it uses as much as digits as its factorization.

81776640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 56448, while the sum is 39.

The square root of 81776640 is about 9043.0437353803. The cubic root of 81776640 is about 434.0533250822.

The spelling of 81776640 in words is "eighty-one million, seven hundred seventy-six thousand, six hundred forty".