3651721 has 4 divisors (see below), whose sum is σ = 3657472. Its totient is φ = 3645972.

The previous prime is 3651673. The next prime is 3651731. The reversal of 3651721 is 1271563.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 3651721 - 2¹³ = 3643529 is a prime.

It is a Duffinian number.

3651721 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3651731) 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, 1785 + ... + 3238.

It is an arithmetic number, because the mean of its divisors is an integer number (914368).

Almost surely, 2^3651721 is an apocalyptic number.

It is an amenable number.

3651721 is a deficient number, since it is larger than the sum of its proper divisors (5751).

3651721 is an equidigital number, since it uses as much as digits as its factorization.

3651721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5750.

The product of its digits is 1260, while the sum is 25.

The square root of 3651721 is about 1910.9476706598. The cubic root of 3651721 is about 153.9923676433.

The spelling of 3651721 in words is "three million, six hundred fifty-one thousand, seven hundred twenty-one".