21138828497 has 2 divisors, whose sum is σ = 21138828498. Its totient is φ = 21138828496.

The previous prime is 21138828457. The next prime is 21138828539. The reversal of 21138828497 is 79482883112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21084201616 + 54626881 = 145204^2 + 7391^2 .

It is a cyclic number.

It is not a de Polignac number, because 21138828497 - 2¹⁸ = 21138566353 is a prime.

It is not a weakly prime, because it can be changed into another prime (21138828427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569414248 + 10569414249.

It is an arithmetic number, because the mean of its divisors is an integer number (10569414249).

Almost surely, 2^21138828497 is an apocalyptic number.

It is an amenable number.

21138828497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138828497 is an equidigital number, since it uses as much as digits as its factorization.

21138828497 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1548288, while the sum is 53.

The spelling of 21138828497 in words is "twenty-one billion, one hundred thirty-eight million, eight hundred twenty-eight thousand, four hundred ninety-seven".