8206721 has 4 divisors (see below), whose sum is σ = 8252244. Its totient is φ = 8161200.

The previous prime is 8206703. The next prime is 8206729. The reversal of 8206721 is 1276028.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 55696 + 8151025 = 236^2 + 2855^2 .

It is a cyclic number.

It is not a de Polignac number, because 8206721 - 2¹⁸ = 7944577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (8206729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22490 + ... + 22851.

It is an arithmetic number, because the mean of its divisors is an integer number (2063061).

Almost surely, 2^8206721 is an apocalyptic number.

It is an amenable number.

8206721 is a deficient number, since it is larger than the sum of its proper divisors (45523).

8206721 is a wasteful number, since it uses less digits than its factorization.

8206721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45522.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 8206721 is about 2864.7375097904. The cubic root of 8206721 is about 201.7080463623.

The spelling of 8206721 in words is "eight million, two hundred six thousand, seven hundred twenty-one".