204123551 has 4 divisors (see below), whose sum is σ = 212998512. Its totient is φ = 195248592.

The previous prime is 204123541. The next prime is 204123583. The reversal of 204123551 is 155321402.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-204123551 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 8874937 = 204123551 / (2 + 0 + 4 + 1 + 2 + 3 + 5 + 5 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204123541) 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, 4437446 + ... + 4437491.

It is an arithmetic number, because the mean of its divisors is an integer number (53249628).

Almost surely, 2^204123551 is an apocalyptic number.

204123551 is a deficient number, since it is larger than the sum of its proper divisors (8874961).

204123551 is an equidigital number, since it uses as much as digits as its factorization.

204123551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8874960.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 204123551 is about 14287.1813525272. The cubic root of 204123551 is about 588.7953501459.

Adding to 204123551 its reverse (155321402), we get a palindrome (359444953).

The spelling of 204123551 in words is "two hundred four million, one hundred twenty-three thousand, five hundred fifty-one".