81777616 has 40 divisors (see below), whose sum is σ = 171879624. Its totient is φ = 37539840.

The previous prime is 81777613. The next prime is 81777623. The reversal of 81777616 is 61677718.

It can be written as a sum of positive squares in 4 ways, for example, as 705600 + 81072016 = 840^2 + 9004^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81777611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7486 + ... + 14818.

Almost surely, 2^81777616 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 81777616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85939812).

81777616 is an abundant number, since it is smaller than the sum of its proper divisors (90102008).

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

81777616 is a wasteful number, since it uses less digits than its factorization.

81777616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7399 (or 7393 counting only the distinct ones).

The product of its digits is 98784, while the sum is 43.

The square root of 81777616 is about 9043.0976993506. The cubic root of 81777616 is about 434.0550518767.

The spelling of 81777616 in words is "eighty-one million, seven hundred seventy-seven thousand, six hundred sixteen".