21207665473 has 2 divisors, whose sum is σ = 21207665474. Its totient is φ = 21207665472.

The previous prime is 21207665449. The next prime is 21207665477. The reversal of 21207665473 is 37456670212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20458439089 + 749226384 = 143033^2 + 27372^2 .

It is a cyclic number.

It is not a de Polignac number, because 21207665473 - 2¹⁷ = 21207534401 is a prime.

It is not a weakly prime, because it can be changed into another prime (21207665477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603832736 + 10603832737.

It is an arithmetic number, because the mean of its divisors is an integer number (10603832737).

Almost surely, 2^21207665473 is an apocalyptic number.

It is an amenable number.

21207665473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21207665473 is an equidigital number, since it uses as much as digits as its factorization.

21207665473 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 423360, while the sum is 43.

The spelling of 21207665473 in words is "twenty-one billion, two hundred seven million, six hundred sixty-five thousand, four hundred seventy-three".