21215404 has 12 divisors (see below), whose sum is σ = 42430864. Its totient is φ = 9092304.

The previous prime is 21215401. The next prime is 21215437. The reversal of 21215404 is 40451212.

21215404 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21215401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 378819 + ... + 378874.

Almost surely, 2^21215404 is an apocalyptic number.

It is an amenable number.

21215404 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21215404 is a wasteful number, since it uses less digits than its factorization.

21215404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 757704 (or 757702 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21215404 is about 4606.0182370460. The cubic root of 21215404 is about 276.8325174524.

Adding to 21215404 its reverse (40451212), we get a palindrome (61666616).

The spelling of 21215404 in words is "twenty-one million, two hundred fifteen thousand, four hundred four".