1556423221 has 4 divisors (see below), whose sum is σ = 1575175392. Its totient is φ = 1537671052.

The previous prime is 1556423201. The next prime is 1556423233. The reversal of 1556423221 is 1223246551.

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 a de Polignac number, because none of the positive numbers 2^k-1556423221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1556423201) 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, 9375961 + ... + 9376126.

It is an arithmetic number, because the mean of its divisors is an integer number (393793848).

Almost surely, 2^1556423221 is an apocalyptic number.

It is an amenable number.

1556423221 is a deficient number, since it is larger than the sum of its proper divisors (18752171).

1556423221 is an equidigital number, since it uses as much as digits as its factorization.

1556423221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18752170.

The product of its digits is 14400, while the sum is 31.

The square root of 1556423221 is about 39451.5300210271. The cubic root of 1556423221 is about 1158.8909388392.

Adding to 1556423221 its reverse (1223246551), we get a palindrome (2779669772).

The spelling of 1556423221 in words is "one billion, five hundred fifty-six million, four hundred twenty-three thousand, two hundred twenty-one".