81351609 has 4 divisors (see below), whose sum is σ = 108468816. Its totient is φ = 54234404.

The previous prime is 81351581. The next prime is 81351629. The reversal of 81351609 is 90615318.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81351609 - 2¹¹ = 81349561 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81351609.

It is not an unprimeable number, because it can be changed into a prime (81351629) 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, 13558599 + ... + 13558604.

It is an arithmetic number, because the mean of its divisors is an integer number (27117204).

Almost surely, 2^81351609 is an apocalyptic number.

It is an amenable number.

81351609 is a deficient number, since it is larger than the sum of its proper divisors (27117207).

81351609 is a wasteful number, since it uses less digits than its factorization.

81351609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27117206.

The product of its (nonzero) digits is 6480, while the sum is 33.

The square root of 81351609 is about 9019.5126808492. The cubic root of 81351609 is about 433.3000265656.

The spelling of 81351609 in words is "eighty-one million, three hundred fifty-one thousand, six hundred nine".