4001821 has 8 divisors (see below), whose sum is σ = 4161024. Its totient is φ = 3844560.

The previous prime is 4001807. The next prime is 4001827. The reversal of 4001821 is 1281004.

4001821 = 44² + 45² + ... + 229².

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 4001821 - 2¹¹ = 3999773 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 4001795 and 4001804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4001827) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4791 + ... + 5563.

It is an arithmetic number, because the mean of its divisors is an integer number (520128).

Almost surely, 2^4001821 is an apocalyptic number.

It is an amenable number.

4001821 is a deficient number, since it is larger than the sum of its proper divisors (159203).

4001821 is a wasteful number, since it uses less digits than its factorization.

4001821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 971.

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 4001821 is about 2000.4551981986. The cubic root of 4001821 is about 158.7641903532.

Adding to 4001821 its reverse (1281004), we get a palindrome (5282825).

The spelling of 4001821 in words is "four million, one thousand, eight hundred twenty-one".