21390612 has 12 divisors (see below), whose sum is σ = 49911456. Its totient is φ = 7130200.

The previous prime is 21390601. The next prime is 21390613. The reversal of 21390612 is 21609312.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390613) 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, 891264 + ... + 891287.

It is an arithmetic number, because the mean of its divisors is an integer number (4159288).

Almost surely, 2^21390612 is an apocalyptic number.

It is an amenable number.

21390612 is an abundant number, since it is smaller than the sum of its proper divisors (28520844).

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

21390612 is a wasteful number, since it uses less digits than its factorization.

21390612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1782558 (or 1782556 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21390612 is about 4624.9985945944. The cubic root of 21390612 is about 277.5925054797.

Adding to 21390612 its reverse (21609312), we get a palindrome (42999924).

The spelling of 21390612 in words is "twenty-one million, three hundred ninety thousand, six hundred twelve".