20911421 has 4 divisors (see below), whose sum is σ = 20957244. Its totient is φ = 20865600.

The previous prime is 20911409. The next prime is 20911427. The reversal of 20911421 is 12411902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2292196 + 18619225 = 1514^2 + 4315^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20911421 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20911393 and 20911402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20911427) 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, 22220 + ... + 23141.

It is an arithmetic number, because the mean of its divisors is an integer number (5239311).

Almost surely, 2^20911421 is an apocalyptic number.

It is an amenable number.

20911421 is a deficient number, since it is larger than the sum of its proper divisors (45823).

20911421 is an equidigital number, since it uses as much as digits as its factorization.

20911421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45822.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 20911421 is about 4572.9007205493. The cubic root of 20911421 is about 275.5039618316.

The spelling of 20911421 in words is "twenty million, nine hundred eleven thousand, four hundred twenty-one".