3635721 has 6 divisors (see below), whose sum is σ = 5251610. Its totient is φ = 2423808.

The previous prime is 3635719. The next prime is 3635729. The reversal of 3635721 is 1275363.

It is a happy number.

3635721 is a `hidden beast` number, since 3 + 635 + 7 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 2595321 + 1040400 = 1611^2 + 1020^2 .

It is not a de Polignac number, because 3635721 - 2¹ = 3635719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3635729) 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, 201976 + ... + 201993.

Almost surely, 2^3635721 is an apocalyptic number.

It is an amenable number.

3635721 is a deficient number, since it is larger than the sum of its proper divisors (1615889).

3635721 is a wasteful number, since it uses less digits than its factorization.

3635721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 403975 (or 403972 counting only the distinct ones).

The product of its digits is 3780, while the sum is 27.

The square root of 3635721 is about 1906.7566703699. The cubic root of 3635721 is about 153.7671327329.

It can be divided in two parts, 3635 and 721, that added together give a square (4356 = 66²).

The spelling of 3635721 in words is "three million, six hundred thirty-five thousand, seven hundred twenty-one".