81904000781 has 8 divisors (see below), whose sum is σ = 84749479200. Its totient is φ = 79059935920.

The previous prime is 81904000769. The next prime is 81904000813. The reversal of 81904000781 is 18700040918.

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 81904000781 - 2²² = 81899806477 is a prime.

It is a super-2 number, since 2×81904000781² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81904000721) 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, 234815 + ... + 467916.

It is an arithmetic number, because the mean of its divisors is an integer number (10593684900).

Almost surely, 2^81904000781 is an apocalyptic number.

81904000781 is the 127988-th centered decagonal number.

It is an amenable number.

81904000781 is a deficient number, since it is larger than the sum of its proper divisors (2845478419).

81904000781 is a wasteful number, since it uses less digits than its factorization.

81904000781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 706779.

The product of its (nonzero) digits is 16128, while the sum is 38.

The spelling of 81904000781 in words is "eighty-one billion, nine hundred four million, seven hundred eighty-one", and thus it is an aban number.