1661782751 has 4 divisors (see below), whose sum is σ = 1661876904. Its totient is φ = 1661688600.

The previous prime is 1661782747. The next prime is 1661782777. The reversal of 1661782751 is 1572871661.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1572871661 = 19 ⋅82782719.

It is a cyclic number.

It is not a de Polignac number, because 1661782751 - 2² = 1661782747 is a prime.

It is a super-2 number, since 2×1661782751² = 5523043823042256002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661782721) 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, 11780 + ... + 58841.

It is an arithmetic number, because the mean of its divisors is an integer number (415469226).

Almost surely, 2^1661782751 is an apocalyptic number.

1661782751 is a deficient number, since it is larger than the sum of its proper divisors (94153).

1661782751 is an equidigital number, since it uses as much as digits as its factorization.

1661782751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94152.

The product of its digits is 141120, while the sum is 44.

The square root of 1661782751 is about 40764.9696553303. The cubic root of 1661782751 is about 1184.4718639723.

The spelling of 1661782751 in words is "one billion, six hundred sixty-one million, seven hundred eighty-two thousand, seven hundred fifty-one".