864789721 has 2 divisors, whose sum is σ = 864789722. Its totient is φ = 864789720.

The previous prime is 864789701. The next prime is 864789787. The reversal of 864789721 is 127987468.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 847683225 + 17106496 = 29115^2 + 4136^2 .

It is a cyclic number.

It is not a de Polignac number, because 864789721 - 2⁵ = 864789689 is a prime.

It is a super-2 number, since 2×864789721² = 1495722523094515682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (864789701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432394860 + 432394861.

It is an arithmetic number, because the mean of its divisors is an integer number (432394861).

Almost surely, 2^864789721 is an apocalyptic number.

It is an amenable number.

864789721 is a deficient number, since it is larger than the sum of its proper divisors (1).

864789721 is an equidigital number, since it uses as much as digits as its factorization.

864789721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1354752, while the sum is 52.

The square root of 864789721 is about 29407.3072721730. The cubic root of 864789721 is about 952.7307289116.

The spelling of 864789721 in words is "eight hundred sixty-four million, seven hundred eighty-nine thousand, seven hundred twenty-one".