21210949957 has 2 divisors, whose sum is σ = 21210949958. Its totient is φ = 21210949956.

The previous prime is 21210949913. The next prime is 21210949967. The reversal of 21210949957 is 75994901212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15276712801 + 5934237156 = 123599^2 + 77034^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210949957 - 2¹⁹ = 21210425669 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21210949957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210949967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605474978 + 10605474979.

It is an arithmetic number, because the mean of its divisors is an integer number (10605474979).

Almost surely, 2^21210949957 is an apocalyptic number.

It is an amenable number.

21210949957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210949957 is an equidigital number, since it uses as much as digits as its factorization.

21210949957 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 408240, while the sum is 49.

The spelling of 21210949957 in words is "twenty-one billion, two hundred ten million, nine hundred forty-nine thousand, nine hundred fifty-seven".