645220273 has 2 divisors, whose sum is σ = 645220274. Its totient is φ = 645220272.

The previous prime is 645220271. The next prime is 645220313. The reversal of 645220273 is 372022546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 559417104 + 85803169 = 23652^2 + 9263^2 .

It is a cyclic number.

It is not a de Polignac number, because 645220273 - 2¹ = 645220271 is a prime.

Together with 645220271, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (645220271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322610136 + 322610137.

It is an arithmetic number, because the mean of its divisors is an integer number (322610137).

Almost surely, 2^645220273 is an apocalyptic number.

It is an amenable number.

645220273 is a deficient number, since it is larger than the sum of its proper divisors (1).

645220273 is an equidigital number, since it uses as much as digits as its factorization.

645220273 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 31.

The square root of 645220273 is about 25401.1864486681. The cubic root of 645220273 is about 864.1106044283.

The spelling of 645220273 in words is "six hundred forty-five million, two hundred twenty thousand, two hundred seventy-three".