20910921 has 4 divisors (see below), whose sum is σ = 27881232. Its totient is φ = 13940612.

The previous prime is 20910919. The next prime is 20910941. The reversal of 20910921 is 12901902.

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 not a de Polignac number, because 20910921 - 2¹ = 20910919 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20910891 and 20910900.

It is not an unprimeable number, because it can be changed into a prime (20910941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3485151 + ... + 3485156.

It is an arithmetic number, because the mean of its divisors is an integer number (6970308).

Almost surely, 2^20910921 is an apocalyptic number.

It is an amenable number.

20910921 is a deficient number, since it is larger than the sum of its proper divisors (6970311).

20910921 is an equidigital number, since it uses as much as digits as its factorization.

20910921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6970310.

The product of its (nonzero) digits is 324, while the sum is 24.

The square root of 20910921 is about 4572.8460503280. The cubic root of 20910921 is about 275.5017660127.

The spelling of 20910921 in words is "twenty million, nine hundred ten thousand, nine hundred twenty-one".