21124155 has 32 divisors (see below), whose sum is σ = 36671040. Its totient is φ = 10383360.

The previous prime is 21124141. The next prime is 21124163. The reversal of 21124155 is 55142112.

It is not a de Polignac number, because 21124155 - 2⁵ = 21124123 is a prime.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 32635 + ... + 33275.

It is an arithmetic number, because the mean of its divisors is an integer number (1145970).

Almost surely, 2^21124155 is an apocalyptic number.

21124155 is a deficient number, since it is larger than the sum of its proper divisors (15546885).

21124155 is an equidigital number, since it uses as much as digits as its factorization.

21124155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 688 (or 662 counting only the distinct ones).

The product of its digits is 400, while the sum is 21.

The square root of 21124155 is about 4596.1021529117. The cubic root of 21124155 is about 276.4350547849.

Adding to 21124155 its reverse (55142112), we get a palindrome (76266267).

The spelling of 21124155 in words is "twenty-one million, one hundred twenty-four thousand, one hundred fifty-five".