645225881 has 4 divisors (see below), whose sum is σ = 652475700. Its totient is φ = 637976064.

The previous prime is 645225851. The next prime is 645225937. The reversal of 645225881 is 188522546.

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 361000000 + 284225881 = 19000^2 + 16859^2 .

It is a cyclic number.

It is not a de Polignac number, because 645225881 - 2²² = 641031577 is a prime.

It is a super-2 number, since 2×645225881² = 832632875024452322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645225851) 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 3 ways as a sum of consecutive naturals, for example, 3624776 + ... + 3624953.

It is an arithmetic number, because the mean of its divisors is an integer number (163118925).

Almost surely, 2^645225881 is an apocalyptic number.

It is an amenable number.

645225881 is a deficient number, since it is larger than the sum of its proper divisors (7249819).

645225881 is an equidigital number, since it uses as much as digits as its factorization.

645225881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7249818.

The product of its digits is 153600, while the sum is 41.

The square root of 645225881 is about 25401.2968369727. The cubic root of 645225881 is about 864.1131079238.

The spelling of 645225881 in words is "six hundred forty-five million, two hundred twenty-five thousand, eight hundred eighty-one".