1661202409 has 2 divisors, whose sum is σ = 1661202410. Its totient is φ = 1661202408.

The previous prime is 1661202391. The next prime is 1661202419. The reversal of 1661202409 is 9042021661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1629898384 + 31304025 = 40372^2 + 5595^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661202409 - 2⁵ = 1661202377 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661202419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830601204 + 830601205.

It is an arithmetic number, because the mean of its divisors is an integer number (830601205).

Almost surely, 2^1661202409 is an apocalyptic number.

It is an amenable number.

1661202409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661202409 is an equidigital number, since it uses as much as digits as its factorization.

1661202409 is an evil number, because the sum of its binary digits is even.

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

The square root of 1661202409 is about 40757.8508878964. The cubic root of 1661202409 is about 1184.3339641164. Note that the first 3 decimals are identical.

The spelling of 1661202409 in words is "one billion, six hundred sixty-one million, two hundred two thousand, four hundred nine".