1231455661 has 4 divisors (see below), whose sum is σ = 1231594524. Its totient is φ = 1231316800.

The previous prime is 1231455593. The next prime is 1231455677. The reversal of 1231455661 is 1665541321.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 518245225 + 713210436 = 22765^2 + 26706^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1231455661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1231455691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55150 + ... + 74191.

It is an arithmetic number, because the mean of its divisors is an integer number (307898631).

Almost surely, 2^1231455661 is an apocalyptic number.

It is an amenable number.

1231455661 is a deficient number, since it is larger than the sum of its proper divisors (138863).

1231455661 is an equidigital number, since it uses as much as digits as its factorization.

1231455661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138862.

The product of its digits is 21600, while the sum is 34.

The square root of 1231455661 is about 35092.1025445897. The cubic root of 1231455661 is about 1071.8637738666.

Adding to 1231455661 its reverse (1665541321), we get a palindrome (2896996982).

The spelling of 1231455661 in words is "one billion, two hundred thirty-one million, four hundred fifty-five thousand, six hundred sixty-one".