21257515403 has 2 divisors, whose sum is σ = 21257515404. Its totient is φ = 21257515402.

The previous prime is 21257515387. The next prime is 21257515421. The reversal of 21257515403 is 30451575212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21257515403 - 2⁴ = 21257515387 is a prime.

It is a super-2 number, since 2×21257515403² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21257515453) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628757701 + 10628757702.

It is an arithmetic number, because the mean of its divisors is an integer number (10628757702).

Almost surely, 2^21257515403 is an apocalyptic number.

21257515403 is a deficient number, since it is larger than the sum of its proper divisors (1).

21257515403 is an equidigital number, since it uses as much as digits as its factorization.

21257515403 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42000, while the sum is 35.

The spelling of 21257515403 in words is "twenty-one billion, two hundred fifty-seven million, five hundred fifteen thousand, four hundred three".