19820908921 has 4 divisors (see below), whose sum is σ = 21622809744. Its totient is φ = 18019008100.

The previous prime is 19820908903. The next prime is 19820908969. The reversal of 19820908921 is 12980902891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19820908921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19820908981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 900950395 + ... + 900950416.

It is an arithmetic number, because the mean of its divisors is an integer number (5405702436).

Almost surely, 2^19820908921 is an apocalyptic number.

19820908921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19820908921 is a deficient number, since it is larger than the sum of its proper divisors (1801900823).

19820908921 is a wasteful number, since it uses less digits than its factorization.

19820908921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1801900822.

The product of its (nonzero) digits is 186624, while the sum is 49.

The spelling of 19820908921 in words is "nineteen billion, eight hundred twenty million, nine hundred eight thousand, nine hundred twenty-one".