21019820091 has 16 divisors (see below), whose sum is σ = 28310734464. Its totient is φ = 13871378304.

The previous prime is 21019820089. The next prime is 21019820117. The reversal of 21019820091 is 19002891012.

It is not a de Polignac number, because 21019820091 - 2¹ = 21019820089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21019820891) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 227400 + ... + 306186.

It is an arithmetic number, because the mean of its divisors is an integer number (1769420904).

Almost surely, 2^21019820091 is an apocalyptic number.

21019820091 is a deficient number, since it is larger than the sum of its proper divisors (7290914373).

21019820091 is a wasteful number, since it uses less digits than its factorization.

21019820091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79690.

The product of its (nonzero) digits is 2592, while the sum is 33.

The spelling of 21019820091 in words is "twenty-one billion, nineteen million, eight hundred twenty thousand, ninety-one".