21203031173 has 2 divisors, whose sum is σ = 21203031174. Its totient is φ = 21203031172.

The previous prime is 21203031169. The next prime is 21203031257. The reversal of 21203031173 is 37113030212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19256280289 + 1946750884 = 138767^2 + 44122^2 .

It is a cyclic number.

It is not a de Polignac number, because 21203031173 - 2² = 21203031169 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21203031673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601515586 + 10601515587.

It is an arithmetic number, because the mean of its divisors is an integer number (10601515587).

Almost surely, 2^21203031173 is an apocalyptic number.

It is an amenable number.

21203031173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203031173 is an equidigital number, since it uses as much as digits as its factorization.

21203031173 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 23.

Adding to 21203031173 its reverse (37113030212), we get a palindrome (58316061385).

The spelling of 21203031173 in words is "twenty-one billion, two hundred three million, thirty-one thousand, one hundred seventy-three".