864513721 has 2 divisors, whose sum is σ = 864513722. Its totient is φ = 864513720.

The previous prime is 864513677. The next prime is 864513731. The reversal of 864513721 is 127315468.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 512388496 + 352125225 = 22636^2 + 18765^2 .

It is a cyclic number.

It is not a de Polignac number, because 864513721 - 2⁷ = 864513593 is a prime.

It is equal to p_44287255 and since 864513721 and 44287255 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (864513731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432256860 + 432256861.

It is an arithmetic number, because the mean of its divisors is an integer number (432256861).

Almost surely, 2^864513721 is an apocalyptic number.

It is an amenable number.

864513721 is a deficient number, since it is larger than the sum of its proper divisors (1).

864513721 is an equidigital number, since it uses as much as digits as its factorization.

864513721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40320, while the sum is 37.

The square root of 864513721 is about 29402.6141864971. The cubic root of 864513721 is about 952.6293625895.

It can be divided in two parts, 8645 and 13721, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 864513721 in words is "eight hundred sixty-four million, five hundred thirteen thousand, seven hundred twenty-one".