81437209 has 16 divisors (see below), whose sum is σ = 94590720. Its totient is φ = 68673600.

The previous prime is 81437207. The next prime is 81437219. The reversal of 81437209 is 90273418.

It is a cyclic number.

It is not a de Polignac number, because 81437209 - 2¹ = 81437207 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81437207) 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, 161652 + ... + 162154.

It is an arithmetic number, because the mean of its divisors is an integer number (5911920).

Almost surely, 2^81437209 is an apocalyptic number.

It is an amenable number.

81437209 is a deficient number, since it is larger than the sum of its proper divisors (13153511).

81437209 is a wasteful number, since it uses less digits than its factorization.

81437209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 81437209 is about 9024.2567006929. The cubic root of 81437209 is about 433.4519493167.

The spelling of 81437209 in words is "eighty-one million, four hundred thirty-seven thousand, two hundred nine".