21113001991 has 2 divisors, whose sum is σ = 21113001992. Its totient is φ = 21113001990.

The previous prime is 21113001983. The next prime is 21113002091. The reversal of 21113001991 is 19910031112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21113001991 - 2³ = 21113001983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21113001971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556500995 + 10556500996.

It is an arithmetic number, because the mean of its divisors is an integer number (10556500996).

Almost surely, 2^21113001991 is an apocalyptic number.

21113001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21113001991 is an equidigital number, since it uses as much as digits as its factorization.

21113001991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 28.

The spelling of 21113001991 in words is "twenty-one billion, one hundred thirteen million, one thousand, nine hundred ninety-one".