21615340 has 12 divisors (see below), whose sum is σ = 45392256. Its totient is φ = 8646128.

The previous prime is 21615337. The next prime is 21615359. The reversal of 21615340 is 4351612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 540364 + ... + 540403.

It is an arithmetic number, because the mean of its divisors is an integer number (3782688).

Almost surely, 2^21615340 is an apocalyptic number.

21615340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21615340 is an abundant number, since it is smaller than the sum of its proper divisors (23776916).

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

21615340 is a wasteful number, since it uses less digits than its factorization.

21615340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1080776 (or 1080774 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21615340 is about 4649.2300437814. The cubic root of 21615340 is about 278.5612421685.

Adding to 21615340 its reverse (4351612), we get a palindrome (25966952).

The spelling of 21615340 in words is "twenty-one million, six hundred fifteen thousand, three hundred forty".