21205473739 has 2 divisors, whose sum is σ = 21205473740. Its totient is φ = 21205473738.

The previous prime is 21205473713. The next prime is 21205473743. The reversal of 21205473739 is 93737450212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21205473739 - 2¹⁷ = 21205342667 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21205473695 and 21205473704.

It is not a weakly prime, because it can be changed into another prime (21205473769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602736869 + 10602736870.

It is an arithmetic number, because the mean of its divisors is an integer number (10602736870).

Almost surely, 2^21205473739 is an apocalyptic number.

21205473739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21205473739 is an equidigital number, since it uses as much as digits as its factorization.

21205473739 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 317520, while the sum is 43.

The spelling of 21205473739 in words is "twenty-one billion, two hundred five million, four hundred seventy-three thousand, seven hundred thirty-nine".