20921804091 has 32 divisors (see below), whose sum is σ = 31560710400. Its totient is φ = 13694022720.

The previous prime is 20921804089. The next prime is 20921804119. The reversal of 20921804091 is 19040812902.

It is not a de Polignac number, because 20921804091 - 2¹ = 20921804089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20921804011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1309471 + ... + 1325351.

It is an arithmetic number, because the mean of its divisors is an integer number (986272200).

Almost surely, 2^20921804091 is an apocalyptic number.

20921804091 is a deficient number, since it is larger than the sum of its proper divisors (10638906309).

20921804091 is a wasteful number, since it uses less digits than its factorization.

20921804091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16776 (or 16770 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The spelling of 20921804091 in words is "twenty billion, nine hundred twenty-one million, eight hundred four thousand, ninety-one".