81520177 has 4 divisors (see below), whose sum is σ = 83508516. Its totient is φ = 79531840.

The previous prime is 81520171. The next prime is 81520199. The reversal of 81520177 is 77102518.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 23775376 + 57744801 = 4876^2 + 7599^2 .

It is a cyclic number.

It is not a de Polignac number, because 81520177 - 2³ = 81520169 is a prime.

It is a super-2 number, since 2×81520177² = 13291078516222658, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81520171) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 994108 + ... + 994189.

It is an arithmetic number, because the mean of its divisors is an integer number (20877129).

Almost surely, 2^81520177 is an apocalyptic number.

It is an amenable number.

81520177 is a deficient number, since it is larger than the sum of its proper divisors (1988339).

81520177 is a wasteful number, since it uses less digits than its factorization.

81520177 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1988338.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 81520177 is about 9028.8524741520. The cubic root of 81520177 is about 433.5990992325.

The spelling of 81520177 in words is "eighty-one million, five hundred twenty thousand, one hundred seventy-seven".