21000091919 has 2 divisors, whose sum is σ = 21000091920. Its totient is φ = 21000091918.

The previous prime is 21000091913. The next prime is 21000091963. The reversal of 21000091919 is 91919000012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000091919 is a prime.

It is a super-2 number, since 2×21000091919² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000091913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500045959 + 10500045960.

It is an arithmetic number, because the mean of its divisors is an integer number (10500045960).

Almost surely, 2^21000091919 is an apocalyptic number.

21000091919 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000091919 is an equidigital number, since it uses as much as digits as its factorization.

21000091919 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1458, while the sum is 32.

The spelling of 21000091919 in words is "twenty-one billion, ninety-one thousand, nine hundred nineteen".