21209874 has 64 divisors (see below), whose sum is σ = 50561280. Its totient is φ = 5806080.

The previous prime is 21209873. The next prime is 21209927. The reversal of 21209874 is 47890212.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21209873) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 187642 + ... + 187754.

It is an arithmetic number, because the mean of its divisors is an integer number (790020).

Almost surely, 2^21209874 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21209874, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25280640).

21209874 is an abundant number, since it is smaller than the sum of its proper divisors (29351406).

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

21209874 is a wasteful number, since it uses less digits than its factorization.

21209874 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21209874 is about 4605.4178963477. The cubic root of 21209874 is about 276.8084623389.

The spelling of 21209874 in words is "twenty-one million, two hundred nine thousand, eight hundred seventy-four".