20856865 has 8 divisors (see below), whose sum is σ = 25076520. Its totient is φ = 16653312.

The previous prime is 20856839. The next prime is 20856877. The reversal of 20856865 is 56865802.

It can be written as a sum of positive squares in 4 ways, for example, as 136161 + 20720704 = 369^2 + 4552^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20856865 - 2¹⁹ = 20332577 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 960 + ... + 6529.

It is an arithmetic number, because the mean of its divisors is an integer number (3134565).

Almost surely, 2^20856865 is an apocalyptic number.

It is an amenable number.

20856865 is a deficient number, since it is larger than the sum of its proper divisors (4219655).

20856865 is an equidigital number, since it uses as much as digits as its factorization.

20856865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8051.

The product of its (nonzero) digits is 115200, while the sum is 40.

The square root of 20856865 is about 4566.9316833077. The cubic root of 20856865 is about 275.2641648948.

The spelling of 20856865 in words is "twenty million, eight hundred fifty-six thousand, eight hundred sixty-five".