21515450 has 24 divisors (see below), whose sum is σ = 43657920. Its totient is φ = 7823600.

The previous prime is 21515449. The next prime is 21515479. The reversal of 21515450 is 5451512.

It is a happy number.

It is a Curzon number.

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 11 ways as a sum of consecutive naturals, for example, 19010 + ... + 20109.

It is an arithmetic number, because the mean of its divisors is an integer number (1819080).

Almost surely, 2^21515450 is an apocalyptic number.

21515450 is an abundant number, since it is smaller than the sum of its proper divisors (22142470).

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

21515450 is a wasteful number, since it uses less digits than its factorization.

21515450 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39142 (or 39137 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 23.

The square root of 21515450 is about 4638.4749648996. The cubic root of 21515450 is about 278.1314786186.

Adding to 21515450 its reverse (5451512), we get a palindrome (26966962).

The spelling of 21515450 in words is "twenty-one million, five hundred fifteen thousand, four hundred fifty".