21210999973 has 2 divisors, whose sum is σ = 21210999974. Its totient is φ = 21210999972.

The previous prime is 21210999917. The next prime is 21210999989. The reversal of 21210999973 is 37999901212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15680549284 + 5530450689 = 125222^2 + 74367^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210999973 - 2²⁹ = 20674129061 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21210999973.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210919973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605499986 + 10605499987.

It is an arithmetic number, because the mean of its divisors is an integer number (10605499987).

Almost surely, 2^21210999973 is an apocalyptic number.

It is an amenable number.

21210999973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210999973 is an equidigital number, since it uses as much as digits as its factorization.

21210999973 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 551124, while the sum is 52.

The spelling of 21210999973 in words is "twenty-one billion, two hundred ten million, nine hundred ninety-nine thousand, nine hundred seventy-three".