842638421 has 2 divisors, whose sum is σ = 842638422. Its totient is φ = 842638420.

The previous prime is 842638393. The next prime is 842638427. The reversal of 842638421 is 124836248.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 678029521 + 164608900 = 26039^2 + 12830^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-842638421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (842638427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 421319210 + 421319211.

It is an arithmetic number, because the mean of its divisors is an integer number (421319211).

Almost surely, 2^842638421 is an apocalyptic number.

It is an amenable number.

842638421 is a deficient number, since it is larger than the sum of its proper divisors (1).

842638421 is an equidigital number, since it uses as much as digits as its factorization.

842638421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 73728, while the sum is 38.

The square root of 842638421 is about 29028.2348929452. The cubic root of 842638421 is about 944.5256415690.

The spelling of 842638421 in words is "eight hundred forty-two million, six hundred thirty-eight thousand, four hundred twenty-one".