21531318 has 16 divisors (see below), whose sum is σ = 43670016. Its totient is φ = 7075880.

The previous prime is 21531317. The next prime is 21531337. The reversal of 21531318 is 81313512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531317) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 24846 + ... + 25697.

It is an arithmetic number, because the mean of its divisors is an integer number (2729376).

Almost surely, 2^21531318 is an apocalyptic number.

21531318 is an abundant number, since it is smaller than the sum of its proper divisors (22138698).

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

21531318 is a wasteful number, since it uses less digits than its factorization.

21531318 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50619.

The product of its digits is 720, while the sum is 24.

The square root of 21531318 is about 4640.1851256173. The cubic root of 21531318 is about 278.1998373370.

The spelling of 21531318 in words is "twenty-one million, five hundred thirty-one thousand, three hundred eighteen".