645661442 has 4 divisors (see below), whose sum is σ = 968492166. Its totient is φ = 322830720.

The previous prime is 645661369. The next prime is 645661531. The reversal of 645661442 is 244166546.

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

It can be written as a sum of positive squares in only one way, i.e., 443481481 + 202179961 = 21059^2 + 14219^2 .

It is a junction number, because it is equal to n+sod(n) for n = 645661396 and 645661405.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161415359 + ... + 161415362.

Almost surely, 2^645661442 is an apocalyptic number.

645661442 is a deficient number, since it is larger than the sum of its proper divisors (322830724).

645661442 is a wasteful number, since it uses less digits than its factorization.

645661442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322830723.

The product of its digits is 138240, while the sum is 38.

The square root of 645661442 is about 25409.8689882494. The cubic root of 645661442 is about 864.3075046054.

The spelling of 645661442 in words is "six hundred forty-five million, six hundred sixty-one thousand, four hundred forty-two".