21143385 has 24 divisors (see below), whose sum is σ = 36755784. Its totient is φ = 11243520.

The previous prime is 21143383. The next prime is 21143411. The reversal of 21143385 is 58334112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 12446784 + 8696601 = 3528^2 + 2949^2 .

It is not a de Polignac number, because 21143385 - 2¹ = 21143383 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21143383) 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 23 ways as a sum of consecutive naturals, for example, 28479 + ... + 29211.

It is an arithmetic number, because the mean of its divisors is an integer number (1531491).

Almost surely, 2^21143385 is an apocalyptic number.

It is an amenable number.

21143385 is a deficient number, since it is larger than the sum of its proper divisors (15612399).

21143385 is a wasteful number, since it uses less digits than its factorization.

21143385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1385 (or 1382 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21143385 is about 4598.1936670828. The cubic root of 21143385 is about 276.5189119279.

Adding to 21143385 its reverse (58334112), we get a palindrome (79477497).

It can be divided in two parts, 21143 and 385, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 21143385 in words is "twenty-one million, one hundred forty-three thousand, three hundred eighty-five".