645566501 has 4 divisors (see below), whose sum is σ = 646526412. Its totient is φ = 644606592.

The previous prime is 645566431. The next prime is 645566503. The reversal of 645566501 is 105665546.

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 305200900 + 340365601 = 17470^2 + 18449^2 .

It is a cyclic number.

It is not a de Polignac number, because 645566501 - 2¹⁰ = 645565477 is a prime.

It is a super-2 number, since 2×645566501² = 833512214426766002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645566503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 478946 + ... + 480291.

It is an arithmetic number, because the mean of its divisors is an integer number (161631603).

Almost surely, 2^645566501 is an apocalyptic number.

It is an amenable number.

645566501 is a deficient number, since it is larger than the sum of its proper divisors (959911).

645566501 is an equidigital number, since it uses as much as digits as its factorization.

645566501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 959910.

The product of its (nonzero) digits is 108000, while the sum is 38.

The square root of 645566501 is about 25408.0007281171. Note that the first 3 decimals coincide. The cubic root of 645566501 is about 864.2651386244.

The spelling of 645566501 in words is "six hundred forty-five million, five hundred sixty-six thousand, five hundred one".