3520721 has 4 divisors (see below), whose sum is σ = 3544500. Its totient is φ = 3496944.

The previous prime is 3520697. The next prime is 3520729. The reversal of 3520721 is 1270253.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1270253 = 67 ⋅18959.

It can be written as a sum of positive squares in 2 ways, for example, as 190096 + 3330625 = 436^2 + 1825^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3520721 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 3520693 and 3520702.

It is not an unprimeable number, because it can be changed into a prime (3520729) 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, 11666 + ... + 11963.

It is an arithmetic number, because the mean of its divisors is an integer number (886125).

Almost surely, 2^3520721 is an apocalyptic number.

It is an amenable number.

3520721 is a deficient number, since it is larger than the sum of its proper divisors (23779).

3520721 is a wasteful number, since it uses less digits than its factorization.

3520721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23778.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 3520721 is about 1876.3584412366. The cubic root of 3520721 is about 152.1284838151.

Adding to 3520721 its reverse (1270253), we get a palindrome (4790974).

The spelling of 3520721 in words is "three million, five hundred twenty thousand, seven hundred twenty-one".