21011819391 has 8 divisors (see below), whose sum is σ = 31128621360. Its totient is φ = 14007879576.

The previous prime is 21011819383. The next prime is 21011819393. The reversal of 21011819391 is 19391811012.

It is not a de Polignac number, because 21011819391 - 2³ = 21011819383 is a prime.

It is a super-2 number, since 2×21011819391² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011819393) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 389107740 + ... + 389107793.

It is an arithmetic number, because the mean of its divisors is an integer number (3891077670).

Almost surely, 2^21011819391 is an apocalyptic number.

21011819391 is a deficient number, since it is larger than the sum of its proper divisors (10116801969).

21011819391 is an equidigital number, since it uses as much as digits as its factorization.

21011819391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778215542 (or 778215536 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 36.

The spelling of 21011819391 in words is "twenty-one billion, eleven million, eight hundred nineteen thousand, three hundred ninety-one".