21131641 has 4 divisors (see below), whose sum is σ = 22050432. Its totient is φ = 20212852.

The previous prime is 21131597. The next prime is 21131651. The reversal of 21131641 is 14613112.

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 a cyclic number.

It is not a de Polignac number, because 21131641 - 2²³ = 12743033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 459361 + ... + 459406.

It is an arithmetic number, because the mean of its divisors is an integer number (5512608).

Almost surely, 2^21131641 is an apocalyptic number.

It is an amenable number.

21131641 is a deficient number, since it is larger than the sum of its proper divisors (918791).

21131641 is an equidigital number, since it uses as much as digits as its factorization.

21131641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 918790.

The product of its digits is 144, while the sum is 19.

The square root of 21131641 is about 4596.9164665023. The cubic root of 21131641 is about 276.4677053756.

Adding to 21131641 its reverse (14613112), we get a palindrome (35744753).

The spelling of 21131641 in words is "twenty-one million, one hundred thirty-one thousand, six hundred forty-one".