21203031257 has 2 divisors, whose sum is σ = 21203031258. Its totient is φ = 21203031256.

The previous prime is 21203031173. The next prime is 21203031277. The reversal of 21203031257 is 75213030212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16489384921 + 4713646336 = 128411^2 + 68656^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21203031257 is a prime.

It is not a weakly prime, because it can be changed into another prime (21203031277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601515628 + 10601515629.

It is an arithmetic number, because the mean of its divisors is an integer number (10601515629).

Almost surely, 2^21203031257 is an apocalyptic number.

It is an amenable number.

21203031257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203031257 is an equidigital number, since it uses as much as digits as its factorization.

21203031257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 26.

Adding to 21203031257 its reverse (75213030212), we get a palindrome (96416061469).

The spelling of 21203031257 in words is "twenty-one billion, two hundred three million, thirty-one thousand, two hundred fifty-seven".