1221931861 has 2 divisors, whose sum is σ = 1221931862. Its totient is φ = 1221931860.

The previous prime is 1221931853. The next prime is 1221931873. The reversal of 1221931861 is 1681391221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1100248900 + 121682961 = 33170^2 + 11031^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221931861 - 2³ = 1221931853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221931891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610965930 + 610965931.

It is an arithmetic number, because the mean of its divisors is an integer number (610965931).

Almost surely, 2^1221931861 is an apocalyptic number.

It is an amenable number.

1221931861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221931861 is an equidigital number, since it uses as much as digits as its factorization.

1221931861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 34.

The square root of 1221931861 is about 34956.1419638953. The cubic root of 1221931861 is about 1069.0934356940.

The spelling of 1221931861 in words is "one billion, two hundred twenty-one million, nine hundred thirty-one thousand, eight hundred sixty-one".