21123201031391 has 2 divisors, whose sum is σ = 21123201031392. Its totient is φ = 21123201031390.

The previous prime is 21123201031223. The next prime is 21123201031463. The reversal of 21123201031391 is 19313010232112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21123201031391 - 2¹⁰ = 21123201030367 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123201001391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561600515695 + 10561600515696.

It is an arithmetic number, because the mean of its divisors is an integer number (10561600515696).

Almost surely, 2^{21123201031391} is an apocalyptic number.

21123201031391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123201031391 is an equidigital number, since it uses as much as digits as its factorization.

21123201031391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

The spelling of 21123201031391 in words is "twenty-one trillion, one hundred twenty-three billion, two hundred one million, thirty-one thousand, three hundred ninety-one".