128643421 has 2 divisors, whose sum is σ = 128643422. Its totient is φ = 128643420.

The previous prime is 128643419. The next prime is 128643457. The reversal of 128643421 is 124346821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 86211225 + 42432196 = 9285^2 + 6514^2 .

It is a cyclic number.

It is not a de Polignac number, because 128643421 - 2¹ = 128643419 is a prime.

Together with 128643419, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128643461) 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, 64321710 + 64321711.

It is an arithmetic number, because the mean of its divisors is an integer number (64321711).

Almost surely, 2^128643421 is an apocalyptic number.

It is an amenable number.

128643421 is a deficient number, since it is larger than the sum of its proper divisors (1).

128643421 is an equidigital number, since it uses as much as digits as its factorization.

128643421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 31.

The square root of 128643421 is about 11342.1083137131. The cubic root of 128643421 is about 504.8114461256.

The spelling of 128643421 in words is "one hundred twenty-eight million, six hundred forty-three thousand, four hundred twenty-one".