21311019971 has 2 divisors, whose sum is σ = 21311019972. Its totient is φ = 21311019970.

The previous prime is 21311019959. The next prime is 21311019997. The reversal of 21311019971 is 17991011312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21311019971 - 2³⁰ = 20237278147 is a prime.

It is not a weakly prime, because it can be changed into another prime (21311019911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655509985 + 10655509986.

It is an arithmetic number, because the mean of its divisors is an integer number (10655509986).

Almost surely, 2^21311019971 is an apocalyptic number.

21311019971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311019971 is an equidigital number, since it uses as much as digits as its factorization.

21311019971 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3402, while the sum is 35.

The spelling of 21311019971 in words is "twenty-one billion, three hundred eleven million, nineteen thousand, nine hundred seventy-one".