20891869 has 4 divisors (see below), whose sum is σ = 20926240. Its totient is φ = 20857500.

The previous prime is 20891831. The next prime is 20891879. The reversal of 20891869 is 96819802.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 96819802 = 2 ⋅48409901.

It is a cyclic number.

It is not a de Polignac number, because 20891869 - 2¹⁷ = 20760797 is a prime.

It is a super-2 number, since 2×20891869² = 872940380626322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20891809) 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, 16257 + ... + 17494.

It is an arithmetic number, because the mean of its divisors is an integer number (5231560).

Almost surely, 2^20891869 is an apocalyptic number.

It is an amenable number.

20891869 is a deficient number, since it is larger than the sum of its proper divisors (34371).

20891869 is an equidigital number, since it uses as much as digits as its factorization.

20891869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34370.

The product of its (nonzero) digits is 62208, while the sum is 43.

The square root of 20891869 is about 4570.7624090517. The cubic root of 20891869 is about 275.4180704399.

The spelling of 20891869 in words is "twenty million, eight hundred ninety-one thousand, eight hundred sixty-nine".