4431213621 has 24 divisors (see below), whose sum is σ = 6799613184. Its totient is φ = 2882083680.

The previous prime is 4431213617. The next prime is 4431213637. The reversal of 4431213621 is 1263121344.

It is a happy number.

4431213621 is a `hidden beast` number, since 4 + 4 + 31 + 2 + 1 + 3 + 621 = 666.

It is not a de Polignac number, because 4431213621 - 2² = 4431213617 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4431213641) 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, 212421 + ... + 232346.

It is an arithmetic number, because the mean of its divisors is an integer number (283317216).

Almost surely, 2^4431213621 is an apocalyptic number.

4431213621 is a gapful number since it is divisible by the number (41) formed by its first and last digit.

It is an amenable number.

4431213621 is a deficient number, since it is larger than the sum of its proper divisors (2368399563).

4431213621 is an equidigital number, since it uses as much as digits as its factorization.

4431213621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444823 (or 444811 counting only the distinct ones).

The product of its digits is 3456, while the sum is 27.

The square root of 4431213621 is about 66567.3615295063. The cubic root of 4431213621 is about 1642.5082604201.

Adding to 4431213621 its reverse (1263121344), we get a palindrome (5694334965).

The spelling of 4431213621 in words is "four billion, four hundred thirty-one million, two hundred thirteen thousand, six hundred twenty-one".