664721419 has 2 divisors, whose sum is σ = 664721420. Its totient is φ = 664721418.

The previous prime is 664721417. The next prime is 664721461. The reversal of 664721419 is 914127466.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 664721419 - 2¹ = 664721417 is a prime.

It is a super-2 number, since 2×664721419² = 883709129754747122, which contains 22 as substring.

Together with 664721417, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (664721417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332360709 + 332360710.

It is an arithmetic number, because the mean of its divisors is an integer number (332360710).

Almost surely, 2^664721419 is an apocalyptic number.

664721419 is a deficient number, since it is larger than the sum of its proper divisors (1).

664721419 is an equidigital number, since it uses as much as digits as its factorization.

664721419 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 664721419 is about 25782.1918967337. The cubic root of 664721419 is about 872.7299718091.

The spelling of 664721419 in words is "six hundred sixty-four million, seven hundred twenty-one thousand, four hundred nineteen".