21624131 has 4 divisors (see below), whose sum is σ = 21668664. Its totient is φ = 21579600.

The previous prime is 21624107. The next prime is 21624137. The reversal of 21624131 is 13142612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21624131 - 2⁶ = 21624067 is a prime.

It is a super-2 number, since 2×21624131² = 935206083010322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21624137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21530 + ... + 22511.

It is an arithmetic number, because the mean of its divisors is an integer number (5417166).

Almost surely, 2^21624131 is an apocalyptic number.

21624131 is a deficient number, since it is larger than the sum of its proper divisors (44533).

21624131 is an equidigital number, since it uses as much as digits as its factorization.

21624131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44532.

The product of its digits is 288, while the sum is 20.

The square root of 21624131 is about 4650.1753730370. The cubic root of 21624131 is about 278.5990008462.

Adding to 21624131 its reverse (13142612), we get a palindrome (34766743).

The spelling of 21624131 in words is "twenty-one million, six hundred twenty-four thousand, one hundred thirty-one".