21005874 has 24 divisors (see below), whose sum is σ = 45685692. Its totient is φ = 6975360.

The previous prime is 21005857. The next prime is 21005891. The reversal of 21005874 is 47850012.

It is an interprime number because it is at equal distance from previous prime (21005857) and next prime (21005891).

It can be written as a sum of positive squares in 2 ways, for example, as 19740249 + 1265625 = 4443^2 + 1125^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2982 + ... + 7134.

Almost surely, 2^21005874 is an apocalyptic number.

21005874 is an abundant number, since it is smaller than the sum of its proper divisors (24679818).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21005874 is a wasteful number, since it uses less digits than its factorization.

21005874 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4442 (or 4439 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21005874 is about 4583.2165560881. The cubic root of 21005874 is about 275.9181389236.

Adding to 21005874 its reverse (47850012), we get a palindrome (68855886).

The spelling of 21005874 in words is "twenty-one million, five thousand, eight hundred seventy-four".