21144923 has 4 divisors (see below), whose sum is σ = 22388760. Its totient is φ = 19901088.

The previous prime is 21144919. The next prime is 21144947. The reversal of 21144923 is 32944112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21144923 - 2² = 21144919 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21144892 and 21144901.

It is not an unprimeable number, because it can be changed into a prime (21144953) 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, 621893 + ... + 621926.

It is an arithmetic number, because the mean of its divisors is an integer number (5597190).

Almost surely, 2^21144923 is an apocalyptic number.

21144923 is a deficient number, since it is larger than the sum of its proper divisors (1243837).

21144923 is a wasteful number, since it uses less digits than its factorization.

21144923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1243836.

The product of its digits is 1728, while the sum is 26.

The square root of 21144923 is about 4598.3609036264. The cubic root of 21144923 is about 276.5256165587.

The spelling of 21144923 in words is "twenty-one million, one hundred forty-four thousand, nine hundred twenty-three".