21001966003493 has 2 divisors, whose sum is σ = 21001966003494. Its totient is φ = 21001966003492.

The previous prime is 21001966003363. The next prime is 21001966003507. The reversal of 21001966003493 is 39430066910012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20949450781249 + 52515222244 = 4577057^2 + 229162^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001966003493 - 2⁸ = 21001966003237 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001966003093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500983001746 + 10500983001747.

It is an arithmetic number, because the mean of its divisors is an integer number (10500983001747).

Almost surely, 2^{21001966003493} is an apocalyptic number.

It is an amenable number.

21001966003493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001966003493 is an equidigital number, since it uses as much as digits as its factorization.

21001966003493 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 209952, while the sum is 44.

The spelling of 21001966003493 in words is "twenty-one trillion, one billion, nine hundred sixty-six million, three thousand, four hundred ninety-three".