81690625 has 12 divisors (see below), whose sum is σ = 102110652. Its totient is φ = 65350000.

The previous prime is 81690619. The next prime is 81690629. The reversal of 81690625 is 52609618.

It can be written as a sum of positive squares in 6 ways, for example, as 60466176 + 21224449 = 7776^2 + 4607^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81690625 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81690629) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9946 + ... + 16195.

It is an arithmetic number, because the mean of its divisors is an integer number (8509221).

It is a Proth number, since it is equal to 2493 ⋅ 2¹⁵ + 1 and 2493 < 2¹⁵.

Almost surely, 2^81690625 is an apocalyptic number.

It is an amenable number.

81690625 is a deficient number, since it is larger than the sum of its proper divisors (20420027).

81690625 is an frugal number, since it uses more digits than its factorization.

81690625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26166 (or 26146 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 81690625 is about 9038.2866186020. The cubic root of 81690625 is about 433.9010884758.

The spelling of 81690625 in words is "eighty-one million, six hundred ninety thousand, six hundred twenty-five".