21144387 has 24 divisors (see below), whose sum is σ = 32005120. Its totient is φ = 12394800.

The previous prime is 21144373. The next prime is 21144419. The reversal of 21144387 is 78344112.

It is not a de Polignac number, because 21144387 - 2⁶ = 21144323 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21144307) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10314 + ... + 12192.

Almost surely, 2^21144387 is an apocalyptic number.

21144387 is a deficient number, since it is larger than the sum of its proper divisors (10860733).

21144387 is a wasteful number, since it uses less digits than its factorization.

21144387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1935 (or 1924 counting only the distinct ones).

The product of its digits is 5376, while the sum is 30.

The square root of 21144387 is about 4598.3026216203. The cubic root of 21144387 is about 276.5232800013.

Adding to 21144387 its reverse (78344112), we get a palindrome (99488499).

The spelling of 21144387 in words is "twenty-one million, one hundred forty-four thousand, three hundred eighty-seven".