255561821 has 4 divisors (see below), whose sum is σ = 256687872. Its totient is φ = 254435772.

The previous prime is 255561811. The next prime is 255561841. The reversal of 255561821 is 128165552.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 255561821 - 2²² = 251367517 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (255561811) 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, 562685 + ... + 563138.

It is an arithmetic number, because the mean of its divisors is an integer number (64171968).

Almost surely, 2^255561821 is an apocalyptic number.

It is an amenable number.

255561821 is a deficient number, since it is larger than the sum of its proper divisors (1126051).

255561821 is a wasteful number, since it uses less digits than its factorization.

255561821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1126050.

The product of its digits is 24000, while the sum is 35.

The square root of 255561821 is about 15986.3010418295. The cubic root of 255561821 is about 634.5979400397.

The spelling of 255561821 in words is "two hundred fifty-five million, five hundred sixty-one thousand, eight hundred twenty-one".