21390657811 has 2 divisors, whose sum is σ = 21390657812. Its totient is φ = 21390657810.

The previous prime is 21390657797. The next prime is 21390657829. The reversal of 21390657811 is 11875609312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21390657811 - 2¹¹ = 21390655763 is a prime.

It is not a weakly prime, because it can be changed into another prime (21390607811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695328905 + 10695328906.

It is an arithmetic number, because the mean of its divisors is an integer number (10695328906).

Almost surely, 2^21390657811 is an apocalyptic number.

21390657811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390657811 is an equidigital number, since it uses as much as digits as its factorization.

21390657811 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90720, while the sum is 43.

The spelling of 21390657811 in words is "twenty-one billion, three hundred ninety million, six hundred fifty-seven thousand, eight hundred eleven".