21405412 has 24 divisors (see below), whose sum is σ = 42928704. Its totient is φ = 9148512.

The previous prime is 21405409. The next prime is 21405427. The reversal of 21405412 is 21450412.

It is a self number, because there is not a number n which added to its sum of digits gives 21405412.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12258 + ... + 13894.

It is an arithmetic number, because the mean of its divisors is an integer number (1788696).

Almost surely, 2^21405412 is an apocalyptic number.

It is an amenable number.

21405412 is an abundant number, since it is smaller than the sum of its proper divisors (21523292).

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

21405412 is a wasteful number, since it uses less digits than its factorization.

21405412 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2115 (or 2113 counting only the distinct ones).

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

The square root of 21405412 is about 4626.5983184193. The cubic root of 21405412 is about 277.6565120936.

Adding to 21405412 its reverse (21450412), we get a palindrome (42855824).

The spelling of 21405412 in words is "twenty-one million, four hundred five thousand, four hundred twelve".