20256643 has 4 divisors (see below), whose sum is σ = 22098168. Its totient is φ = 18415120.

The previous prime is 20256637. The next prime is 20256659. The reversal of 20256643 is 34665202.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20256643 - 2¹³ = 20248451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20256143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 920746 + ... + 920767.

It is an arithmetic number, because the mean of its divisors is an integer number (5524542).

Almost surely, 2^20256643 is an apocalyptic number.

20256643 is a deficient number, since it is larger than the sum of its proper divisors (1841525).

20256643 is a wasteful number, since it uses less digits than its factorization.

20256643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1841524.

The product of its (nonzero) digits is 8640, while the sum is 28.

The square root of 20256643 is about 4500.7380505868. The cubic root of 20256643 is about 272.5978909307.

It can be divided in two parts, 2025 and 6643, that added together give a palindrome (8668).

The spelling of 20256643 in words is "twenty million, two hundred fifty-six thousand, six hundred forty-three".