21390657829 has 2 divisors, whose sum is σ = 21390657830. Its totient is φ = 21390657828.

The previous prime is 21390657811. The next prime is 21390657853. The reversal of 21390657829 is 92875609312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16537445604 + 4853212225 = 128598^2 + 69665^2 .

It is a cyclic number.

It is not a de Polignac number, because 21390657829 - 2⁵ = 21390657797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21390657229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695328914 + 10695328915.

It is an arithmetic number, because the mean of its divisors is an integer number (10695328915).

Almost surely, 2^21390657829 is an apocalyptic number.

It is an amenable number.

21390657829 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390657829 is an equidigital number, since it uses as much as digits as its factorization.

21390657829 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1632960, while the sum is 52.

The spelling of 21390657829 in words is "twenty-one billion, three hundred ninety million, six hundred fifty-seven thousand, eight hundred twenty-nine".