81551821897729 has 8 divisors (see below), whose sum is σ = 82390400069120. Its totient is φ = 80714143974816.

The previous prime is 81551821897613. The next prime is 81551821897753. The reversal of 81551821897729 is 92779812815518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81551821897729 - 2¹⁹ = 81551821373441 is a prime.

It is a super-2 number, since 2×81551821897729² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81551821897759) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 224880012 + ... + 225242365.

It is an arithmetic number, because the mean of its divisors is an integer number (10298800008640).

Almost surely, 2^{81551821897729} is an apocalyptic number.

It is an amenable number.

81551821897729 is a deficient number, since it is larger than the sum of its proper divisors (838578171391).

81551821897729 is a wasteful number, since it uses less digits than its factorization.

81551821897729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450124239.

The product of its digits is 203212800, while the sum is 73.

The spelling of 81551821897729 in words is "eighty-one trillion, five hundred fifty-one billion, eight hundred twenty-one million, eight hundred ninety-seven thousand, seven hundred twenty-nine".