642516421 has 2 divisors, whose sum is σ = 642516422. Its totient is φ = 642516420.

The previous prime is 642516397. The next prime is 642516439. The reversal of 642516421 is 124615246.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 498852225 + 143664196 = 22335^2 + 11986^2 .

It is a cyclic number.

It is not a de Polignac number, because 642516421 - 2⁵ = 642516389 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642516451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321258210 + 321258211.

It is an arithmetic number, because the mean of its divisors is an integer number (321258211).

Almost surely, 2^642516421 is an apocalyptic number.

It is an amenable number.

642516421 is a deficient number, since it is larger than the sum of its proper divisors (1).

642516421 is an equidigital number, since it uses as much as digits as its factorization.

642516421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 31.

The square root of 642516421 is about 25347.9076256799. The cubic root of 642516421 is about 862.9018707235.

The spelling of 642516421 in words is "six hundred forty-two million, five hundred sixteen thousand, four hundred twenty-one".