1643421251 has 2 divisors, whose sum is σ = 1643421252. Its totient is φ = 1643421250.

The previous prime is 1643421181. The next prime is 1643421281. The reversal of 1643421251 is 1521243461.

It is a strong prime.

It is an emirp because it is prime and its reverse (1521243461) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1643421251 is a prime.

It is not a weakly prime, because it can be changed into another prime (1643421281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821710625 + 821710626.

It is an arithmetic number, because the mean of its divisors is an integer number (821710626).

Almost surely, 2^1643421251 is an apocalyptic number.

1643421251 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643421251 is an equidigital number, since it uses as much as digits as its factorization.

1643421251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 29.

The square root of 1643421251 is about 40539.1323414796. The cubic root of 1643421251 is about 1180.0931773113.

The spelling of 1643421251 in words is "one billion, six hundred forty-three million, four hundred twenty-one thousand, two hundred fifty-one".