642021851 has 2 divisors, whose sum is σ = 642021852. Its totient is φ = 642021850.

The previous prime is 642021841. The next prime is 642021859. The reversal of 642021851 is 158120246.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642021851 is a prime.

It is a super-2 number, since 2×642021851² = 824384114322932402, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (642021859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321010925 + 321010926.

It is an arithmetic number, because the mean of its divisors is an integer number (321010926).

Almost surely, 2^642021851 is an apocalyptic number.

642021851 is a deficient number, since it is larger than the sum of its proper divisors (1).

642021851 is an equidigital number, since it uses as much as digits as its factorization.

642021851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 642021851 is about 25338.1501100613. The cubic root of 642021851 is about 862.6804107937.

The spelling of 642021851 in words is "six hundred forty-two million, twenty-one thousand, eight hundred fifty-one".