6443721 has 6 divisors (see below), whose sum is σ = 9307610. Its totient is φ = 4295808.

The previous prime is 6443719. The next prime is 6443737. The reversal of 6443721 is 1273446.

It can be written as a sum of positive squares in only one way, i.e., 6125625 + 318096 = 2475^2 + 564^2 .

It is not a de Polignac number, because 6443721 - 2¹ = 6443719 is a prime.

It is a d-powerful number, because it can be written as 6 + 4² + 4⁷ + 3¹² + 7⁸ + 2¹⁷ + 1 .

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (6443791) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 357976 + ... + 357993.

Almost surely, 2^6443721 is an apocalyptic number.

It is an amenable number.

6443721 is a deficient number, since it is larger than the sum of its proper divisors (2863889).

6443721 is a wasteful number, since it uses less digits than its factorization.

6443721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 715975 (or 715972 counting only the distinct ones).

The product of its digits is 4032, while the sum is 27.

The square root of 6443721 is about 2538.4485419248. The cubic root of 6443721 is about 186.0853753049.

The spelling of 6443721 in words is "six million, four hundred forty-three thousand, seven hundred twenty-one".