81859409 has 4 divisors (see below), whose sum is σ = 81890304. Its totient is φ = 81828516.

The previous prime is 81859381. The next prime is 81859417. The reversal of 81859409 is 90495818.

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 81859409 - 2⁸ = 81859153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81859409.

It is not an unprimeable number, because it can be changed into a prime (81859439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11057 + ... + 16910.

It is an arithmetic number, because the mean of its divisors is an integer number (20472576).

Almost surely, 2^81859409 is an apocalyptic number.

It is an amenable number.

81859409 is a deficient number, since it is larger than the sum of its proper divisors (30895).

81859409 is a wasteful number, since it uses less digits than its factorization.

81859409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30894.

The product of its (nonzero) digits is 103680, while the sum is 44.

The square root of 81859409 is about 9047.6189685464. The cubic root of 81859409 is about 434.1997158924.

The spelling of 81859409 in words is "eighty-one million, eight hundred fifty-nine thousand, four hundred nine".