20821859 has 4 divisors (see below), whose sum is σ = 20834016. Its totient is φ = 20809704.

The previous prime is 20821849. The next prime is 20821873. The reversal of 20821859 is 95812802.

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 20821859 - 2²⁴ = 4044643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20821849) 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, 2984 + ... + 7109.

It is an arithmetic number, because the mean of its divisors is an integer number (5208504).

Almost surely, 2^20821859 is an apocalyptic number.

20821859 is a deficient number, since it is larger than the sum of its proper divisors (12157).

20821859 is a wasteful number, since it uses less digits than its factorization.

20821859 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12156.

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 20821859 is about 4563.0975225169. The cubic root of 20821859 is about 275.1100782456.

The spelling of 20821859 in words is "twenty million, eight hundred twenty-one thousand, eight hundred fifty-nine".