1491839561 has 4 divisors (see below), whose sum is σ = 1493735952. Its totient is φ = 1489943172.

The previous prime is 1491839551. The next prime is 1491839563. The reversal of 1491839561 is 1659381941.

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 1491839561 - 2⁶ = 1491839497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1491839563) 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, 947015 + ... + 948588.

It is an arithmetic number, because the mean of its divisors is an integer number (373433988).

Almost surely, 2^1491839561 is an apocalyptic number.

It is an amenable number.

1491839561 is a deficient number, since it is larger than the sum of its proper divisors (1896391).

1491839561 is an equidigital number, since it uses as much as digits as its factorization.

1491839561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1896390.

The product of its digits is 233280, while the sum is 47.

The square root of 1491839561 is about 38624.3389716899. The cubic root of 1491839561 is about 1142.6346065390.

The spelling of 1491839561 in words is "one billion, four hundred ninety-one million, eight hundred thirty-nine thousand, five hundred sixty-one".