21315646 has 32 divisors (see below), whose sum is σ = 36088416. Its totient is φ = 9360000.

The previous prime is 21315643. The next prime is 21315647. The reversal of 21315646 is 64651312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315643) 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, 117676 + ... + 117856.

It is an arithmetic number, because the mean of its divisors is an integer number (1127763).

Almost surely, 2^21315646 is an apocalyptic number.

21315646 is a deficient number, since it is larger than the sum of its proper divisors (14772770).

21315646 is a wasteful number, since it uses less digits than its factorization.

21315646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348.

The product of its digits is 4320, while the sum is 28.

The square root of 21315646 is about 4616.8870464849. The cubic root of 21315646 is about 277.2678403478.

Adding to 21315646 its reverse (64651312), we get a palindrome (85966958).

It can be divided in two parts, 2131 and 5646, that added together give a palindrome (7777).

The spelling of 21315646 in words is "twenty-one million, three hundred fifteen thousand, six hundred forty-six".