20858721 has 8 divisors (see below), whose sum is σ = 29951040. Its totient is φ = 12836112.

The previous prime is 20858707. The next prime is 20858729. The reversal of 20858721 is 12785802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20858721 - 2⁵ = 20858689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20858729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 267381 + ... + 267458.

It is an arithmetic number, because the mean of its divisors is an integer number (3743880).

Almost surely, 2^20858721 is an apocalyptic number.

It is an amenable number.

20858721 is a deficient number, since it is larger than the sum of its proper divisors (9092319).

20858721 is a wasteful number, since it uses less digits than its factorization.

20858721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534855.

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 20858721 is about 4567.1348786739. The cubic root of 20858721 is about 275.2723296747.

The spelling of 20858721 in words is "twenty million, eight hundred fifty-eight thousand, seven hundred twenty-one".