1661212305 has 24 divisors (see below), whose sum is σ = 2888837952. Its totient is φ = 883086624.

The previous prime is 1661212303. The next prime is 1661212339. The reversal of 1661212305 is 5032121661.

1661212305 is a `hidden beast` number, since 1 + 6 + 612 + 12 + 30 + 5 = 666.

It is not a de Polignac number, because 1661212305 - 2¹ = 1661212303 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1661212303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 46309 + ... + 73938.

It is an arithmetic number, because the mean of its divisors is an integer number (120368248).

Almost surely, 2^1661212305 is an apocalyptic number.

1661212305 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661212305 is a deficient number, since it is larger than the sum of its proper divisors (1227625647).

1661212305 is a wasteful number, since it uses less digits than its factorization.

1661212305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120565 (or 120562 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 1661212305 is about 40757.9722876396. The cubic root of 1661212305 is about 1184.3363158558.

Adding to 1661212305 its reverse (5032121661), we get a palindrome (6693333966).

The spelling of 1661212305 in words is "one billion, six hundred sixty-one million, two hundred twelve thousand, three hundred five".