21581412 has 12 divisors (see below), whose sum is σ = 50356656. Its totient is φ = 7193800.

The previous prime is 21581389. The next prime is 21581431. The reversal of 21581412 is 21418512.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 899214 + ... + 899237.

It is an arithmetic number, because the mean of its divisors is an integer number (4196388).

Almost surely, 2^21581412 is an apocalyptic number.

It is an amenable number.

21581412 is an abundant number, since it is smaller than the sum of its proper divisors (28775244).

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

21581412 is a wasteful number, since it uses less digits than its factorization.

21581412 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1798458 (or 1798456 counting only the distinct ones).

The product of its digits is 640, while the sum is 24.

The square root of 21581412 is about 4645.5798346385. The cubic root of 21581412 is about 278.4154201890.

Adding to 21581412 its reverse (21418512), we get a palindrome (42999924).

It can be divided in two parts, 2158 and 1412, that added together give a triangular number (3570 = T₈₄).

The spelling of 21581412 in words is "twenty-one million, five hundred eighty-one thousand, four hundred twelve".