1661312461 has 4 divisors (see below), whose sum is σ = 1670010624. Its totient is φ = 1652614300.

The previous prime is 1661312459. The next prime is 1661312467. The reversal of 1661312461 is 1642131661.

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 an emirpimes, since its reverse is a distinct semiprime: 1642131661 = 809 ⋅2029829.

It is a cyclic number.

It is not a de Polignac number, because 1661312461 - 2¹ = 1661312459 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 (1661312467) 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, 4348795 + ... + 4349176.

It is an arithmetic number, because the mean of its divisors is an integer number (417502656).

Almost surely, 2^1661312461 is an apocalyptic number.

It is an amenable number.

1661312461 is a deficient number, since it is larger than the sum of its proper divisors (8698163).

1661312461 is an equidigital number, since it uses as much as digits as its factorization.

1661312461 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8698162.

The product of its digits is 5184, while the sum is 31.

The square root of 1661312461 is about 40759.2009367210. The cubic root of 1661312461 is about 1184.3601169485.

The spelling of 1661312461 in words is "one billion, six hundred sixty-one million, three hundred twelve thousand, four hundred sixty-one".