20856251 has 8 divisors (see below), whose sum is σ = 22543920. Its totient is φ = 19180512.

The previous prime is 20856223. The next prime is 20856259. The reversal of 20856251 is 15265802.

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

It is not a de Polignac number, because 20856251 - 2¹⁴ = 20839867 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20856259) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 845 + ... + 6513.

It is an arithmetic number, because the mean of its divisors is an integer number (2817990).

Almost surely, 2^20856251 is an apocalyptic number.

20856251 is a deficient number, since it is larger than the sum of its proper divisors (1687669).

20856251 is a wasteful number, since it uses less digits than its factorization.

20856251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5965.

The product of its (nonzero) digits is 4800, while the sum is 29.

The square root of 20856251 is about 4566.8644604367. The cubic root of 20856251 is about 275.2614637242.

The spelling of 20856251 in words is "twenty million, eight hundred fifty-six thousand, two hundred fifty-one".