21204534 has 16 divisors (see below), whose sum is σ = 45671472. Its totient is φ = 6524448.

The previous prime is 21204509. The next prime is 21204553. The reversal of 21204534 is 43540212.

It is a self number, because there is not a number n which added to its sum of digits gives 21204534.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 135849 + ... + 136004.

It is an arithmetic number, because the mean of its divisors is an integer number (2854467).

Almost surely, 2^21204534 is an apocalyptic number.

21204534 is an abundant number, since it is smaller than the sum of its proper divisors (24466938).

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

21204534 is a wasteful number, since it uses less digits than its factorization.

21204534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271871.

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21204534 is about 4604.8381079035. The cubic root of 21204534 is about 276.7852297436.

Adding to 21204534 its reverse (43540212), we get a palindrome (64744746).

The spelling of 21204534 in words is "twenty-one million, two hundred four thousand, five hundred thirty-four".