861821629 has 2 divisors, whose sum is σ = 861821630. Its totient is φ = 861821628.

The previous prime is 861821593. The next prime is 861821641. The reversal of 861821629 is 926128168.

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., 536848900 + 324972729 = 23170^2 + 18027^2 .

It is a cyclic number.

It is not a de Polignac number, because 861821629 - 2²¹ = 859724477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861821659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430910814 + 430910815.

It is an arithmetic number, because the mean of its divisors is an integer number (430910815).

Almost surely, 2^861821629 is an apocalyptic number.

It is an amenable number.

861821629 is a deficient number, since it is larger than the sum of its proper divisors (1).

861821629 is an equidigital number, since it uses as much as digits as its factorization.

861821629 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82944, while the sum is 43.

The square root of 861821629 is about 29356.7986844615. The cubic root of 861821629 is about 951.6395064988.

The spelling of 861821629 in words is "eight hundred sixty-one million, eight hundred twenty-one thousand, six hundred twenty-nine".