20643855 has 8 divisors (see below), whose sum is σ = 33030192. Its totient is φ = 11010048.

The previous prime is 20643851. The next prime is 20643893. The reversal of 20643855 is 55834602.

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

It is not a de Polignac number, because 20643855 - 2² = 20643851 is a prime.

It is a super-2 number, since 2×20643855² = 852337498522050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20643851) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 688114 + ... + 688143.

It is an arithmetic number, because the mean of its divisors is an integer number (4128774).

Almost surely, 2^20643855 is an apocalyptic number.

20643855 is a deficient number, since it is larger than the sum of its proper divisors (12386337).

20643855 is a wasteful number, since it uses less digits than its factorization.

20643855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1376265.

The product of its (nonzero) digits is 28800, while the sum is 33.

The square root of 20643855 is about 4543.5509241121. The cubic root of 20643855 is about 274.3238706761.

The spelling of 20643855 in words is "twenty million, six hundred forty-three thousand, eight hundred fifty-five".