81666530 has 24 divisors (see below), whose sum is σ = 161580636. Its totient is φ = 29696480.

The previous prime is 81666509. The next prime is 81666551. The reversal of 81666530 is 3566618.

It is an interprime number because it is at equal distance from previous prime (81666509) and next prime (81666551).

It can be written as a sum of positive squares in 2 ways, for example, as 79192201 + 2474329 = 8899^2 + 1573^2 .

It is a Curzon number.

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 11 ways as a sum of consecutive naturals, for example, 32537 + ... + 34956.

Almost surely, 2^81666530 is an apocalyptic number.

81666530 is a deficient number, since it is larger than the sum of its proper divisors (79914106).

81666530 is a wasteful number, since it uses less digits than its factorization.

81666530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67522 (or 67511 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 81666530 is about 9036.9535796086. The cubic root of 81666530 is about 433.8584239522.

The spelling of 81666530 in words is "eighty-one million, six hundred sixty-six thousand, five hundred thirty".