21906643906253 has 2 divisors, whose sum is σ = 21906643906254. Its totient is φ = 21906643906252.

The previous prime is 21906643906153. The next prime is 21906643906283. The reversal of 21906643906253 is 35260934660912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16378516573444 + 5528127332809 = 4047038^2 + 2351197^2 .

It is a cyclic number.

It is not a de Polignac number, because 21906643906253 - 2⁸ = 21906643905997 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21906643906283) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953321953126 + 10953321953127.

It is an arithmetic number, because the mean of its divisors is an integer number (10953321953127).

Almost surely, 2^{21906643906253} is an apocalyptic number.

It is an amenable number.

21906643906253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906643906253 is an equidigital number, since it uses as much as digits as its factorization.

21906643906253 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12597120, while the sum is 56.

The spelling of 21906643906253 in words is "twenty-one trillion, nine hundred six billion, six hundred forty-three million, nine hundred six thousand, two hundred fifty-three".