1581961 has 4 divisors (see below), whose sum is σ = 1633024. Its totient is φ = 1530900.

The previous prime is 1581949. The next prime is 1582001. The reversal of 1581961 is 1691851.

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 1581961 - 2⁵ = 1581929 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 51031 = 1581961 / (1 + 5 + 8 + 1 + 9 + 6 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1581911) 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, 25485 + ... + 25546.

It is an arithmetic number, because the mean of its divisors is an integer number (408256).

2^1581961 is an apocalyptic number.

It is an amenable number.

1581961 is a deficient number, since it is larger than the sum of its proper divisors (51063).

1581961 is an equidigital number, since it uses as much as digits as its factorization.

1581961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51062.

The product of its digits is 2160, while the sum is 31.

The square root of 1581961 is about 1257.7603110291. The cubic root of 1581961 is about 116.5194942419.

The spelling of 1581961 in words is "one million, five hundred eighty-one thousand, nine hundred sixty-one".