81609172 has 12 divisors (see below), whose sum is σ = 144127060. Its totient is φ = 40430016.

The previous prime is 81609167. The next prime is 81609191. The reversal of 81609172 is 27190618.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 67963536 + 13645636 = 8244^2 + 3694^2 .

It is a congruent 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 3 ways as a sum of consecutive naturals, for example, 93153 + ... + 94024.

Almost surely, 2^81609172 is an apocalyptic number.

It is an amenable number.

81609172 is a deficient number, since it is larger than the sum of its proper divisors (62517888).

81609172 is a wasteful number, since it uses less digits than its factorization.

81609172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187290 (or 187288 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 81609172 is about 9033.7794969769. The cubic root of 81609172 is about 433.7568275383.

The spelling of 81609172 in words is "eighty-one million, six hundred nine thousand, one hundred seventy-two".