21203031491 has 2 divisors, whose sum is σ = 21203031492. Its totient is φ = 21203031490.

The previous prime is 21203031449. The next prime is 21203031497. The reversal of 21203031491 is 19413030212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21203031491 - 2¹⁰ = 21203030467 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21203031491.

It is not a weakly prime, because it can be changed into another prime (21203031497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601515745 + 10601515746.

It is an arithmetic number, because the mean of its divisors is an integer number (10601515746).

Almost surely, 2^21203031491 is an apocalyptic number.

21203031491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203031491 is an equidigital number, since it uses as much as digits as its factorization.

21203031491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 26.

The spelling of 21203031491 in words is "twenty-one billion, two hundred three million, thirty-one thousand, four hundred ninety-one".