81690785856 has 63 divisors (see below), whose sum is σ = 234171551341. Its totient is φ = 27227975424.

The previous prime is 81690785843. The next prime is 81690785861. The reversal of 81690785856 is 65858709618.

The square root of 81690785856 is 285816.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 27494945856 + 54195840000 = 165816^2 + 232800^2 .

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81690785793 and 81690785802.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 6853630 + ... + 6865538.

Almost surely, 2^81690785856 is an apocalyptic number.

81690785856 is the 285816-th square number.

It is an amenable number.

81690785856 is an abundant number, since it is smaller than the sum of its proper divisors (152480765485).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81690785856 is an frugal number, since it uses more digits than its factorization.

81690785856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23836 (or 11914 counting only the distinct ones).

The product of its (nonzero) digits is 29030400, while the sum is 63.

The spelling of 81690785856 in words is "eighty-one billion, six hundred ninety million, seven hundred eighty-five thousand, eight hundred fifty-six".