20421646630261 has 2 divisors, whose sum is σ = 20421646630262. Its totient is φ = 20421646630260.

The previous prime is 20421646630237. The next prime is 20421646630267. The reversal of 20421646630261 is 16203664612402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19129855265361 + 1291791364900 = 4373769^2 + 1136570^2 .

It is a cyclic number.

It is not a de Polignac number, because 20421646630261 - 2²⁷ = 20421512412533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20421646630267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210823315130 + 10210823315131.

It is an arithmetic number, because the mean of its divisors is an integer number (10210823315131).

Almost surely, 2^{20421646630261} is an apocalyptic number.

It is an amenable number.

20421646630261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20421646630261 is an equidigital number, since it uses as much as digits as its factorization.

20421646630261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 497664, while the sum is 43.

The spelling of 20421646630261 in words is "twenty trillion, four hundred twenty-one billion, six hundred forty-six million, six hundred thirty thousand, two hundred sixty-one".