1561554251 has 4 divisors (see below), whose sum is σ = 1561633632. Its totient is φ = 1561474872.

The previous prime is 1561554223. The next prime is 1561554301. The reversal of 1561554251 is 1524551651.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1561554251 - 2²⁶ = 1494445387 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561554221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14285 + ... + 57681.

It is an arithmetic number, because the mean of its divisors is an integer number (390408408).

Almost surely, 2^1561554251 is an apocalyptic number.

1561554251 is a deficient number, since it is larger than the sum of its proper divisors (79381).

1561554251 is an equidigital number, since it uses as much as digits as its factorization.

1561554251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79380.

The product of its digits is 30000, while the sum is 35.

The square root of 1561554251 is about 39516.5060575957. The cubic root of 1561554251 is about 1160.1630396578.

The spelling of 1561554251 in words is "one billion, five hundred sixty-one million, five hundred fifty-four thousand, two hundred fifty-one".