21120400243 has 4 divisors (see below), whose sum is σ = 21120942960. Its totient is φ = 21119857528.

The previous prime is 21120400229. The next prime is 21120400267. The reversal of 21120400243 is 34200402112.

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 21120400243 - 2⁹ = 21120399731 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21120400243.

It is not an unprimeable number, because it can be changed into a prime (21120400283) 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, 208063 + ... + 292456.

It is an arithmetic number, because the mean of its divisors is an integer number (5280235740).

Almost surely, 2^21120400243 is an apocalyptic number.

21120400243 is a deficient number, since it is larger than the sum of its proper divisors (542717).

21120400243 is an equidigital number, since it uses as much as digits as its factorization.

21120400243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 542716.

The product of its (nonzero) digits is 384, while the sum is 19.

Adding to 21120400243 its reverse (34200402112), we get a palindrome (55320802355).

The spelling of 21120400243 in words is "twenty-one billion, one hundred twenty million, four hundred thousand, two hundred forty-three".