81566903 has 16 divisors (see below), whose sum is σ = 90484992. Its totient is φ = 72912000.

The previous prime is 81566873. The next prime is 81566909. The reversal of 81566903 is 30966518.

It is a cyclic number.

It is not a de Polignac number, because 81566903 - 2¹⁶ = 81501367 is a prime.

It is a super-2 number, since 2×81566903² = 13306319330022818, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81566909) 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, 262118 + ... + 262428.

It is an arithmetic number, because the mean of its divisors is an integer number (5655312).

Almost surely, 2^81566903 is an apocalyptic number.

81566903 is a deficient number, since it is larger than the sum of its proper divisors (8918089).

81566903 is a wasteful number, since it uses less digits than its factorization.

81566903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 81566903 is about 9031.4396969697. The cubic root of 81566903 is about 433.6819273230.

The spelling of 81566903 in words is "eighty-one million, five hundred sixty-six thousand, nine hundred three".