81631225 has 27 divisors (see below), whose sum is σ = 110402253.
Its totient is φ = 59847840.
The previous prime is 81631219. The next prime is 81631267. The reversal of 81631225 is 52213618.
It can be divided in two parts, 816 and 31225, that added together give a square (32041 = 1792).
The square root of 81631225 is 9035.
It is a perfect power (a square), and thus also a powerful number.
It can be written as a sum of positive squares in 4 ways, for example, as 21040569 + 60590656 = 4587^2 + 7784^2
It is not a de Polignac number, because 81631225 - 23 = 81631217 is a prime.
It is a junction number, because it is equal to n+sod(n) for n = 81631193 and 81631202.
It is an unprimeable number.
It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 587206 + ... + 587344.
Almost surely, 281631225 is an apocalyptic number.
81631225 is the 9035-th square number.
81631225 is the 4518-th centered octagonal number.
It is an amenable number.
81631225 is a deficient number, since it is larger than the sum of its proper divisors (28771028).
81631225 is a wasteful number, since it uses less digits than its factorization.
81631225 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 314 (or 157 counting only the distinct ones).
The product of its digits is 2880, while the sum is 28.
The cubic root of 81631225 is about 433.7958949519.
The spelling of 81631225 in words is "eighty-one million, six hundred thirty-one thousand, two hundred twenty-five".