21157841 has 4 divisors (see below), whose sum is σ = 21840384. Its totient is φ = 20475300.

The previous prime is 21157831. The next prime is 21157867. The reversal of 21157841 is 14875112.

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 21157841 - 2²² = 16963537 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21157831) 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, 341225 + ... + 341286.

It is an arithmetic number, because the mean of its divisors is an integer number (5460096).

Almost surely, 2^21157841 is an apocalyptic number.

It is an amenable number.

21157841 is a deficient number, since it is larger than the sum of its proper divisors (682543).

21157841 is an equidigital number, since it uses as much as digits as its factorization.

21157841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 682542.

The product of its digits is 2240, while the sum is 29.

The square root of 21157841 is about 4599.7653201006. The cubic root of 21157841 is about 276.5819173978.

The spelling of 21157841 in words is "twenty-one million, one hundred fifty-seven thousand, eight hundred forty-one".