4001221521 has 24 divisors (see below), whose sum is σ = 6307138656. Its totient is φ = 2424143040.

The previous prime is 4001221501. The next prime is 4001221561. The reversal of 4001221521 is 1251221004.

It is not a de Polignac number, because 4001221521 - 2¹⁸ = 4000959377 is a prime.

It is a super-2 number, since 2×4001221521² = 32019547320227106882, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 4001221494 and 4001221503.

It is not an unprimeable number, because it can be changed into a prime (4001221501) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 398266 + ... + 408188.

It is an arithmetic number, because the mean of its divisors is an integer number (262797444).

Almost surely, 2^4001221521 is an apocalyptic number.

It is an amenable number.

4001221521 is a deficient number, since it is larger than the sum of its proper divisors (2305917135).

4001221521 is a wasteful number, since it uses less digits than its factorization.

4001221521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14013 (or 14010 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 4001221521 is about 63255.2094376424. The cubic root of 4001221521 is about 1587.5626224992.

Adding to 4001221521 its reverse (1251221004), we get a palindrome (5252442525).

It can be divided in two parts, 4001 and 221521, that added together give a palindrome (225522).

The spelling of 4001221521 in words is "four billion, one million, two hundred twenty-one thousand, five hundred twenty-one".