194218021 has 2 divisors, whose sum is σ = 194218022. Its totient is φ = 194218020.

The previous prime is 194218009. The next prime is 194218099. The reversal of 194218021 is 120812491.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168350625 + 25867396 = 12975^2 + 5086^2 .

It is a cyclic number.

It is not a de Polignac number, because 194218021 - 2⁷ = 194217893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (194218001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97109010 + 97109011.

It is an arithmetic number, because the mean of its divisors is an integer number (97109011).

Almost surely, 2^194218021 is an apocalyptic number.

It is an amenable number.

194218021 is a deficient number, since it is larger than the sum of its proper divisors (1).

194218021 is an equidigital number, since it uses as much as digits as its factorization.

194218021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 194218021 is about 13936.2125773110. The cubic root of 194218021 is about 579.1128142557.

The spelling of 194218021 in words is "one hundred ninety-four million, two hundred eighteen thousand, twenty-one".