81690669 has 18 divisors (see below), whose sum is σ = 120830190. Its totient is φ = 53183088.

The previous prime is 81690659. The next prime is 81690689. The reversal of 81690669 is 96609618.

It can be written as a sum of positive squares in only one way, i.e., 81540900 + 149769 = 9030^2 + 387^2 .

It is not a de Polignac number, because 81690669 - 2¹² = 81686573 is a prime.

It is a super-2 number, since 2×81690669² = 13346730803335122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81690619) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 14187 + ... + 19095.

Almost surely, 2^81690669 is an apocalyptic number.

It is an amenable number.

81690669 is a deficient number, since it is larger than the sum of its proper divisors (39139521).

81690669 is a wasteful number, since it uses less digits than its factorization.

81690669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5001 (or 4955 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 45.

The square root of 81690669 is about 9038.2890526913. The cubic root of 81690669 is about 433.9011663781.

The spelling of 81690669 in words is "eighty-one million, six hundred ninety thousand, six hundred sixty-nine".