1581725641 has 4 divisors (see below), whose sum is σ = 1581830784. Its totient is φ = 1581620500.

The previous prime is 1581725609. The next prime is 1581725659. The reversal of 1581725641 is 1465271851.

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, 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 1581725641 - 2⁵ = 1581725609 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1581725594 and 1581725603.

It is not an unprimeable number, because it can be changed into a prime (1581705641) 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, 25285 + ... + 61666.

It is an arithmetic number, because the mean of its divisors is an integer number (395457696).

Almost surely, 2^1581725641 is an apocalyptic number.

It is an amenable number.

1581725641 is a deficient number, since it is larger than the sum of its proper divisors (105143).

1581725641 is an equidigital number, since it uses as much as digits as its factorization.

1581725641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105142.

The product of its digits is 67200, while the sum is 40.

The square root of 1581725641 is about 39770.9145104811. The cubic root of 1581725641 is about 1165.1371549181.

The spelling of 1581725641 in words is "one billion, five hundred eighty-one million, seven hundred twenty-five thousand, six hundred forty-one".