21381206 has 32 divisors (see below), whose sum is σ = 42342912. Its totient is φ = 7839360.

The previous prime is 21381203. The next prime is 21381209. The reversal of 21381206 is 60218312.

It is an interprime number because it is at equal distance from previous prime (21381203) and next prime (21381209).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1466 + ... + 6701.

It is an arithmetic number, because the mean of its divisors is an integer number (1323216).

Almost surely, 2^21381206 is an apocalyptic number.

21381206 is a deficient number, since it is larger than the sum of its proper divisors (20961706).

21381206 is a wasteful number, since it uses less digits than its factorization.

21381206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8204.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21381206 is about 4623.9816176105. The cubic root of 21381206 is about 277.5518113360.

Adding to 21381206 its reverse (60218312), we get a palindrome (81599518).

The spelling of 21381206 in words is "twenty-one million, three hundred eighty-one thousand, two hundred six".