20891819 has 4 divisors (see below), whose sum is σ = 22498896. Its totient is φ = 19284744.

The previous prime is 20891809. The next prime is 20891831. The reversal of 20891819 is 91819802.

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

It is a cyclic number.

It is not a de Polignac number, because 20891819 - 2²⁴ = 4114603 is a prime.

It is a super-2 number, since 2×20891819² = 872936202257522, which contains 22 as substring.

It is a Duffinian 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, 803519 + ... + 803544.

It is an arithmetic number, because the mean of its divisors is an integer number (5624724).

Almost surely, 2^20891819 is an apocalyptic number.

20891819 is a deficient number, since it is larger than the sum of its proper divisors (1607077).

20891819 is a wasteful number, since it uses less digits than its factorization.

20891819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1607076.

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 20891819 is about 4570.7569395014. The cubic root of 20891819 is about 275.4178507226.

The spelling of 20891819 in words is "twenty million, eight hundred ninety-one thousand, eight hundred nineteen".