21004172 has 24 divisors (see below), whose sum is σ = 42422016. Its totient is φ = 8913168.

The previous prime is 21004169. The next prime is 21004183. The reversal of 21004172 is 27140012.

It is a self number, because there is not a number n which added to its sum of digits gives 21004172.

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, 758 + ... + 6525.

It is an arithmetic number, because the mean of its divisors is an integer number (1767584).

Almost surely, 2^21004172 is an apocalyptic number.

It is an amenable number.

21004172 is an abundant number, since it is smaller than the sum of its proper divisors (21417844).

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

21004172 is a wasteful number, since it uses less digits than its factorization.

21004172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7397 (or 7395 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21004172 is about 4583.0308748687. The cubic root of 21004172 is about 275.9106866373.

Adding to 21004172 its reverse (27140012), we get a palindrome (48144184).

The spelling of 21004172 in words is "twenty-one million, four thousand, one hundred seventy-two".