21123155 has 8 divisors (see below), whose sum is σ = 26682000. Its totient is φ = 16009056.

The previous prime is 21123149. The next prime is 21123161. The reversal of 21123155 is 55132112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21123149) and next prime (21123161).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123155 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 111080 + ... + 111269.

It is an arithmetic number, because the mean of its divisors is an integer number (3335250).

Almost surely, 2^21123155 is an apocalyptic number.

21123155 is a deficient number, since it is larger than the sum of its proper divisors (5558845).

21123155 is a wasteful number, since it uses less digits than its factorization.

21123155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222373.

The product of its digits is 300, while the sum is 20.

The square root of 21123155 is about 4595.9933637898. The cubic root of 21123155 is about 276.4306926472.

Adding to 21123155 its reverse (55132112), we get a palindrome (76255267).

The spelling of 21123155 in words is "twenty-one million, one hundred twenty-three thousand, one hundred fifty-five".