645556051 has 4 divisors (see below), whose sum is σ = 737778352. Its totient is φ = 553333752.

The previous prime is 645556039. The next prime is 645556061. The reversal of 645556051 is 150655546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 150655546 = 2 ⋅75327773.

It is a cyclic number.

It is not a de Polignac number, because 645556051 - 2⁷ = 645555923 is a prime.

It is a super-2 number, since 2×645556051² = 833485229965429202, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645556051.

It is not an unprimeable number, because it can be changed into a prime (645556001) 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, 46111140 + ... + 46111153.

It is an arithmetic number, because the mean of its divisors is an integer number (184444588).

Almost surely, 2^645556051 is an apocalyptic number.

645556051 is a deficient number, since it is larger than the sum of its proper divisors (92222301).

645556051 is an equidigital number, since it uses as much as digits as its factorization.

645556051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92222300.

The product of its (nonzero) digits is 90000, while the sum is 37.

The square root of 645556051 is about 25407.7950833991. The cubic root of 645556051 is about 864.2604752167.

The spelling of 645556051 in words is "six hundred forty-five million, five hundred fifty-six thousand, fifty-one".