16666254821 has 2 divisors, whose sum is σ = 16666254822. Its totient is φ = 16666254820.

The previous prime is 16666254817. The next prime is 16666254881. The reversal of 16666254821 is 12845266661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9151792225 + 7514462596 = 95665^2 + 86686^2 .

It is a cyclic number.

It is not a de Polignac number, because 16666254821 - 2² = 16666254817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16666254881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8333127410 + 8333127411.

It is an arithmetic number, because the mean of its divisors is an integer number (8333127411).

Almost surely, 2^16666254821 is an apocalyptic number.

It is an amenable number.

16666254821 is a deficient number, since it is larger than the sum of its proper divisors (1).

16666254821 is an equidigital number, since it uses as much as digits as its factorization.

16666254821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 829440, while the sum is 47.

The spelling of 16666254821 in words is "sixteen billion, six hundred sixty-six million, two hundred fifty-four thousand, eight hundred twenty-one".