7191221861 has 2 divisors, whose sum is σ = 7191221862. Its totient is φ = 7191221860.

The previous prime is 7191221801. The next prime is 7191221879. The reversal of 7191221861 is 1681221917.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7177308961 + 13912900 = 84719^2 + 3730^2 .

It is an emirp because it is prime and its reverse (1681221917) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7191221861 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7191221801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3595610930 + 3595610931.

It is an arithmetic number, because the mean of its divisors is an integer number (3595610931).

Almost surely, 2^7191221861 is an apocalyptic number.

It is an amenable number.

7191221861 is a deficient number, since it is larger than the sum of its proper divisors (1).

7191221861 is an equidigital number, since it uses as much as digits as its factorization.

7191221861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 38.

The square root of 7191221861 is about 84801.0722868526. The cubic root of 7191221861 is about 1930.1937093374.

The spelling of 7191221861 in words is "seven billion, one hundred ninety-one million, two hundred twenty-one thousand, eight hundred sixty-one".