81573355815 has 32 divisors (see below), whose sum is σ = 157936988160. Its totient is φ = 35097106944.

The previous prime is 81573355793. The next prime is 81573355837. The reversal of 81573355815 is 51855337518.

It is an interprime number because it is at equal distance from previous prime (81573355793) and next prime (81573355837).

It is not a de Polignac number, because 81573355815 - 2⁵ = 81573355783 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22847895 + ... + 22851464.

It is an arithmetic number, because the mean of its divisors is an integer number (4935530880).

Almost surely, 2^81573355815 is an apocalyptic number.

81573355815 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81573355815 is a deficient number, since it is larger than the sum of its proper divisors (76363632345).

81573355815 is a wasteful number, since it uses less digits than its factorization.

81573355815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45699391.

The product of its digits is 2520000, while the sum is 51.

The spelling of 81573355815 in words is "eighty-one billion, five hundred seventy-three million, three hundred fifty-five thousand, eight hundred fifteen".