8725721 has 4 divisors (see below), whose sum is σ = 8770212. Its totient is φ = 8681232.

The previous prime is 8725699. The next prime is 8725733. The reversal of 8725721 is 1275278.

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 8179600 + 546121 = 2860^2 + 739^2 .

It is a cyclic number.

It is not a de Polignac number, because 8725721 - 2⁶ = 8725657 is a prime.

It is a super-2 number, since 2×8725721² = 152276413939682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8725021) 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, 21950 + ... + 22343.

It is an arithmetic number, because the mean of its divisors is an integer number (2192553).

Almost surely, 2^8725721 is an apocalyptic number.

It is an amenable number.

8725721 is a deficient number, since it is larger than the sum of its proper divisors (44491).

8725721 is a wasteful number, since it uses less digits than its factorization.

8725721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44490.

The product of its digits is 7840, while the sum is 32.

The square root of 8725721 is about 2953.9331407464. The cubic root of 8725721 is about 205.8734966547.

Adding to 8725721 its sum of digits (32), we get a triangular number (8725753 = T₄₁₇₇).

It can be divided in two parts, 87257 and 21, that added together give a palindrome (87278).

The spelling of 8725721 in words is "eight million, seven hundred twenty-five thousand, seven hundred twenty-one".