81668553 has 16 divisors (see below), whose sum is σ = 112907520. Its totient is φ = 52446464.

The previous prime is 81668519. The next prime is 81668557. The reversal of 81668553 is 35586618.

It is a cyclic number.

It is not a de Polignac number, because 81668553 - 2¹³ = 81660361 is a prime.

It is a super-2 number, since 2×81668553² = 13339505098227618, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81668557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50800 + ... + 52382.

It is an arithmetic number, because the mean of its divisors is an integer number (7056720).

Almost surely, 2^81668553 is an apocalyptic number.

It is an amenable number.

81668553 is a deficient number, since it is larger than the sum of its proper divisors (31238967).

81668553 is a wasteful number, since it uses less digits than its factorization.

81668553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2208.

The product of its digits is 172800, while the sum is 42.

The square root of 81668553 is about 9037.0655082278. The cubic root of 81668553 is about 433.8620063596.

The spelling of 81668553 in words is "eighty-one million, six hundred sixty-eight thousand, five hundred fifty-three".