81551821897727 has 32 divisors (see below), whose sum is σ = 83325626588160. Its totient is φ = 79792192076800.

The previous prime is 81551821897613. The next prime is 81551821897753. The reversal of 81551821897727 is 72779812815518.

It is not a de Polignac number, because 81551821897727 - 2⁴⁶ = 11183077720063 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81551821897127) 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, 30972965603 + ... + 30972968235.

It is an arithmetic number, because the mean of its divisors is an integer number (2603925830880).

Almost surely, 2^{81551821897727} is an apocalyptic number.

81551821897727 is a deficient number, since it is larger than the sum of its proper divisors (1773804690433).

81551821897727 is a wasteful number, since it uses less digits than its factorization.

81551821897727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5503.

The product of its digits is 158054400, while the sum is 71.

The spelling of 81551821897727 in words is "eighty-one trillion, five hundred fifty-one billion, eight hundred twenty-one million, eight hundred ninety-seven thousand, seven hundred twenty-seven".