21538641 has 4 divisors (see below), whose sum is σ = 28718192. Its totient is φ = 14359092.

The previous prime is 21538597. The next prime is 21538651. The reversal of 21538641 is 14683512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21538641 - 2¹⁴ = 21522257 is a prime.

It is a super-2 number, since 2×21538641² = 927826112253762, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21538599 and 21538608.

It is not an unprimeable number, because it can be changed into a prime (21538651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3589771 + ... + 3589776.

It is an arithmetic number, because the mean of its divisors is an integer number (7179548).

Almost surely, 2^21538641 is an apocalyptic number.

It is an amenable number.

21538641 is a deficient number, since it is larger than the sum of its proper divisors (7179551).

21538641 is an equidigital number, since it uses as much as digits as its factorization.

21538641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7179550.

The product of its digits is 5760, while the sum is 30.

The square root of 21538641 is about 4640.9741434315. The cubic root of 21538641 is about 278.2313732063.

The spelling of 21538641 in words is "twenty-one million, five hundred thirty-eight thousand, six hundred forty-one".