81613907890 has 8 divisors (see below), whose sum is σ = 146905034220. Its totient is φ = 32645563152.

The previous prime is 81613907813. The next prime is 81613907909. The reversal of 81613907890 is 9870931618.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 76446167121 + 5167740769 = 276489^2 + 71887^2 .

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

It is a super-2 number, since 2×81613907890² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4080695385 + ... + 4080695404.

Almost surely, 2^81613907890 is an apocalyptic number.

81613907890 is a deficient number, since it is larger than the sum of its proper divisors (65291126330).

81613907890 is a wasteful number, since it uses less digits than its factorization.

81613907890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8161390796.

The product of its (nonzero) digits is 653184, while the sum is 52.

The spelling of 81613907890 in words is "eighty-one billion, six hundred thirteen million, nine hundred seven thousand, eight hundred ninety".