81225009 has 24 divisors (see below), whose sum is σ = 119208960. Its totient is φ = 53288928.

The previous prime is 81225007. The next prime is 81225013. The reversal of 81225009 is 90052218.

It is not a de Polignac number, because 81225009 - 2¹ = 81225007 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81225007) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 204399 + ... + 204795.

It is an arithmetic number, because the mean of its divisors is an integer number (4967040).

Almost surely, 2^81225009 is an apocalyptic number.

It is an amenable number.

81225009 is a deficient number, since it is larger than the sum of its proper divisors (37983951).

81225009 is a wasteful number, since it uses less digits than its factorization.

81225009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 709 (or 706 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 81225009 is about 9012.4918307869. The cubic root of 81225009 is about 433.0751415907.

It can be divided in two parts, 8122500 and 9, that multiplied together give a square (73102500 = 8550²).

The spelling of 81225009 in words is "eighty-one million, two hundred twenty-five thousand, nine".