81621365 has 32 divisors (see below), whose sum is σ = 119702016. Its totient is φ = 52208640.

The previous prime is 81621361. The next prime is 81621383. The reversal of 81621365 is 56312618.

It is a happy number.

It is not a de Polignac number, because 81621365 - 2² = 81621361 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81621361) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 31769 + ... + 34241.

It is an arithmetic number, because the mean of its divisors is an integer number (3740688).

Almost surely, 2^81621365 is an apocalyptic number.

It is an amenable number.

81621365 is a deficient number, since it is larger than the sum of its proper divisors (38080651).

81621365 is a wasteful number, since it uses less digits than its factorization.

81621365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2549.

The product of its digits is 8640, while the sum is 32.

The square root of 81621365 is about 9034.4543277389. The cubic root of 81621365 is about 433.7784285973.

The spelling of 81621365 in words is "eighty-one million, six hundred twenty-one thousand, three hundred sixty-five".