81866473 has 6 divisors (see below), whose sum is σ = 88648494. Its totient is φ = 75568896.

The previous prime is 81866471. The next prime is 81866489. The reversal of 81866473 is 37466818.

It can be written as a sum of positive squares in 3 ways, for example, as 12027024 + 69839449 = 3468^2 + 8357^2 .

It is not a de Polignac number, because 81866473 - 2¹ = 81866471 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81866471) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 242040 + ... + 242377.

It is an arithmetic number, because the mean of its divisors is an integer number (14774749).

Almost surely, 2^81866473 is an apocalyptic number.

It is an amenable number.

81866473 is a deficient number, since it is larger than the sum of its proper divisors (6782021).

81866473 is a wasteful number, since it uses less digits than its factorization.

81866473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 484443 (or 484430 counting only the distinct ones).

The product of its digits is 193536, while the sum is 43.

The square root of 81866473 is about 9048.0093390756. The cubic root of 81866473 is about 434.2122051860.

The spelling of 81866473 in words is "eighty-one million, eight hundred sixty-six thousand, four hundred seventy-three".