645682421 has 2 divisors, whose sum is σ = 645682422. Its totient is φ = 645682420.

The previous prime is 645682403. The next prime is 645682469. The reversal of 645682421 is 124286546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 342435025 + 303247396 = 18505^2 + 17414^2 .

It is a cyclic number.

It is not a de Polignac number, because 645682421 - 2¹⁰ = 645681397 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645682021) 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 as a sum of consecutive naturals, namely, 322841210 + 322841211.

It is an arithmetic number, because the mean of its divisors is an integer number (322841211).

Almost surely, 2^645682421 is an apocalyptic number.

It is an amenable number.

645682421 is a deficient number, since it is larger than the sum of its proper divisors (1).

645682421 is an equidigital number, since it uses as much as digits as its factorization.

645682421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 92160, while the sum is 38.

The square root of 645682421 is about 25410.2817969420. The cubic root of 645682421 is about 864.3168656057.

The spelling of 645682421 in words is "six hundred forty-five million, six hundred eighty-two thousand, four hundred twenty-one".