81693648 has 120 divisors (see below), whose sum is σ = 238250376. Its totient is φ = 26112000.

The previous prime is 81693641. The next prime is 81693659. The reversal of 81693648 is 84639618.

It can be written as a sum of positive squares in 4 ways, for example, as 15303744 + 66389904 = 3912^2 + 8148^2 .

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81693641) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 596236 + ... + 596372.

Almost surely, 2^81693648 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 81693648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119125188).

81693648 is an abundant number, since it is smaller than the sum of its proper divisors (156556728).

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

81693648 is a wasteful number, since it uses less digits than its factorization.

81693648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293 (or 284 counting only the distinct ones).

The product of its digits is 248832, while the sum is 45.

The square root of 81693648 is about 9038.4538500786. The cubic root of 81693648 is about 433.9064406478.

The spelling of 81693648 in words is "eighty-one million, six hundred ninety-three thousand, six hundred forty-eight".