21315550 has 12 divisors (see below), whose sum is σ = 39647016. Its totient is φ = 8526200.

The previous prime is 21315521. The next prime is 21315557. The reversal of 21315550 is 5551312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315557) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 213106 + ... + 213205.

It is an arithmetic number, because the mean of its divisors is an integer number (3303918).

Almost surely, 2^21315550 is an apocalyptic number.

21315550 is a deficient number, since it is larger than the sum of its proper divisors (18331466).

21315550 is a wasteful number, since it uses less digits than its factorization.

21315550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 426323 (or 426318 counting only the distinct ones).

The product of its (nonzero) digits is 750, while the sum is 22.

The square root of 21315550 is about 4616.8766498576. The cubic root of 21315550 is about 277.2674241003.

Adding to 21315550 its reverse (5551312), we get a palindrome (26866862).

The spelling of 21315550 in words is "twenty-one million, three hundred fifteen thousand, five hundred fifty".