21205890490297 has 2 divisors, whose sum is σ = 21205890490298. Its totient is φ = 21205890490296.

The previous prime is 21205890490283. The next prime is 21205890490361. The reversal of 21205890490297 is 79209409850212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18834940325776 + 2370950164521 = 4339924^2 + 1539789^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21205890490297 is a prime.

It is a super-2 number, since 2×21205890490297² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21205890490597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602945245148 + 10602945245149.

It is an arithmetic number, because the mean of its divisors is an integer number (10602945245149).

Almost surely, 2^{21205890490297} is an apocalyptic number.

It is an amenable number.

21205890490297 is a deficient number, since it is larger than the sum of its proper divisors (1).

21205890490297 is an equidigital number, since it uses as much as digits as its factorization.

21205890490297 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6531840, while the sum is 58.

The spelling of 21205890490297 in words is "twenty-one trillion, two hundred five billion, eight hundred ninety million, four hundred ninety thousand, two hundred ninety-seven".