1661644747 has 4 divisors (see below), whose sum is σ = 1899022576. Its totient is φ = 1424266920.

The previous prime is 1661644739. The next prime is 1661644757. The reversal of 1661644747 is 7474461661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7474461661 = 19 ⋅393392719.

It is a cyclic number.

It is not a de Polignac number, because 1661644747 - 2³ = 1661644739 is a prime.

It is a super-2 number, since 2×1661644747² = 5522126530465388018, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1661644697 and 1661644706.

It is not an unprimeable number, because it can be changed into a prime (1661644727) 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, 118688904 + ... + 118688917.

It is an arithmetic number, because the mean of its divisors is an integer number (474755644).

Almost surely, 2^1661644747 is an apocalyptic number.

1661644747 is a deficient number, since it is larger than the sum of its proper divisors (237377829).

1661644747 is an equidigital number, since it uses as much as digits as its factorization.

1661644747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237377828.

The product of its digits is 677376, while the sum is 46.

The square root of 1661644747 is about 40763.2769413844. The cubic root of 1661644747 is about 1184.4390746120.

The spelling of 1661644747 in words is "one billion, six hundred sixty-one million, six hundred forty-four thousand, seven hundred forty-seven".