20905851 has 16 divisors (see below), whose sum is σ = 28872704. Its totient is φ = 13444704.

The previous prime is 20905831. The next prime is 20905861. The reversal of 20905851 is 15850902.

It is not a de Polignac number, because 20905851 - 2¹⁰ = 20904827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20905831) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13356 + ... + 14838.

It is an arithmetic number, because the mean of its divisors is an integer number (1804544).

Almost surely, 2^20905851 is an apocalyptic number.

20905851 is a deficient number, since it is larger than the sum of its proper divisors (7966853).

20905851 is a wasteful number, since it uses less digits than its factorization.

20905851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1650.

The product of its (nonzero) digits is 3600, while the sum is 30.

The square root of 20905851 is about 4572.2916573640. The cubic root of 20905851 is about 275.4794984321.

The spelling of 20905851 in words is "twenty million, nine hundred five thousand, eight hundred fifty-one".