1661645819 has 2 divisors, whose sum is σ = 1661645820. Its totient is φ = 1661645818.

The previous prime is 1661645809. The next prime is 1661645927. The reversal of 1661645819 is 9185461661.

It is a weak prime.

It is an emirp because it is prime and its reverse (9185461661) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661645819 is a prime.

It is a super-2 number, since 2×1661645819² = 5522133655600361522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1661645809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830822909 + 830822910.

It is an arithmetic number, because the mean of its divisors is an integer number (830822910).

Almost surely, 2^1661645819 is an apocalyptic number.

1661645819 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661645819 is an equidigital number, since it uses as much as digits as its factorization.

1661645819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 47.

The square root of 1661645819 is about 40763.2900904723. The cubic root of 1661645819 is about 1184.4393293231.

The spelling of 1661645819 in words is "one billion, six hundred sixty-one million, six hundred forty-five thousand, eight hundred nineteen".