81551225 has 24 divisors (see below), whose sum is σ = 115909248. Its totient is φ = 55756800.

The previous prime is 81551221. The next prime is 81551233. The reversal of 81551225 is 52215518.

It is not a de Polignac number, because 81551225 - 2² = 81551221 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81551221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 111812 + ... + 112538.

It is an arithmetic number, because the mean of its divisors is an integer number (4829552).

Almost surely, 2^81551225 is an apocalyptic number.

It is an amenable number.

81551225 is a deficient number, since it is larger than the sum of its proper divisors (34358023).

81551225 is a wasteful number, since it uses less digits than its factorization.

81551225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1385 (or 1380 counting only the distinct ones).

The product of its digits is 4000, while the sum is 29.

The square root of 81551225 is about 9030.5716873297. The cubic root of 81551225 is about 433.6541394961.

The spelling of 81551225 in words is "eighty-one million, five hundred fifty-one thousand, two hundred twenty-five".