21287349 has 12 divisors (see below), whose sum is σ = 32557356. Its totient is φ = 13356672.

The previous prime is 21287347. The next prime is 21287389. The reversal of 21287349 is 94378212.

It can be written as a sum of positive squares in 2 ways, for example, as 19980900 + 1306449 = 4470^2 + 1143^2 .

It is not a de Polignac number, because 21287349 - 2¹ = 21287347 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287347) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 69414 + ... + 69719.

It is an arithmetic number, because the mean of its divisors is an integer number (2713113).

Almost surely, 2^21287349 is an apocalyptic number.

It is an amenable number.

21287349 is a deficient number, since it is larger than the sum of its proper divisors (11270007).

21287349 is a wasteful number, since it uses less digits than its factorization.

21287349 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139156 (or 139153 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21287349 is about 4613.8215180044. The cubic root of 21287349 is about 277.1450929148.

The spelling of 21287349 in words is "twenty-one million, two hundred eighty-seven thousand, three hundred forty-nine".