861397921 has 2 divisors, whose sum is σ = 861397922. Its totient is φ = 861397920.

The previous prime is 861397903. The next prime is 861397937. The reversal of 861397921 is 129793168.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 823403025 + 37994896 = 28695^2 + 6164^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-861397921 is a prime.

It is not a weakly prime, because it can be changed into another prime (861397721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430698960 + 430698961.

It is an arithmetic number, because the mean of its divisors is an integer number (430698961).

Almost surely, 2^861397921 is an apocalyptic number.

It is an amenable number.

861397921 is a deficient number, since it is larger than the sum of its proper divisors (1).

861397921 is an equidigital number, since it uses as much as digits as its factorization.

861397921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 46.

The square root of 861397921 is about 29349.5812746962. The cubic root of 861397921 is about 951.4835255100.

The spelling of 861397921 in words is "eight hundred sixty-one million, three hundred ninety-seven thousand, nine hundred twenty-one".