20969909 has 4 divisors (see below), whose sum is σ = 21313740. Its totient is φ = 20626080.

The previous prime is 20969903. The next prime is 20969953. The reversal of 20969909 is 90996902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90996902 = 2 ⋅45498451.

It can be written as a sum of positive squares in 2 ways, for example, as 1697809 + 19272100 = 1303^2 + 4390^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20969909 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20969909.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20969903) 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, 171824 + ... + 171945.

It is an arithmetic number, because the mean of its divisors is an integer number (5328435).

Almost surely, 2^20969909 is an apocalyptic number.

It is an amenable number.

20969909 is a deficient number, since it is larger than the sum of its proper divisors (343831).

20969909 is an equidigital number, since it uses as much as digits as its factorization.

20969909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 343830.

The product of its (nonzero) digits is 78732, while the sum is 44.

The square root of 20969909 is about 4579.2913207177. The cubic root of 20969909 is about 275.7605787942.

The spelling of 20969909 in words is "twenty million, nine hundred sixty-nine thousand, nine hundred nine".