81581396 has 12 divisors (see below), whose sum is σ = 153749652. Its totient is φ = 37652928.

The previous prime is 81581393. The next prime is 81581399. The reversal of 81581396 is 69318518.

It is an interprime number because it is at equal distance from previous prime (81581393) and next prime (81581399).

It can be written as a sum of positive squares in 2 ways, for example, as 54228496 + 27352900 = 7364^2 + 5230^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81581393) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 784385 + ... + 784488.

It is an arithmetic number, because the mean of its divisors is an integer number (12812471).

Almost surely, 2^81581396 is an apocalyptic number.

It is an amenable number.

81581396 is a deficient number, since it is larger than the sum of its proper divisors (72168256).

81581396 is a wasteful number, since it uses less digits than its factorization.

81581396 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1568890 (or 1568888 counting only the distinct ones).

The product of its digits is 51840, while the sum is 41.

The square root of 81581396 is about 9032.2420251010. The cubic root of 81581396 is about 433.7076116782.

The spelling of 81581396 in words is "eighty-one million, five hundred eighty-one thousand, three hundred ninety-six".