21540915 has 24 divisors (see below), whose sum is σ = 40732848. Its totient is φ = 10443840.

The previous prime is 21540901. The next prime is 21540917. The reversal of 21540915 is 51904512.

It is not a de Polignac number, because 21540915 - 2⁷ = 21540787 is a prime.

It is a super-2 number, since 2×21540915² = 928022038074450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21540917) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21264 + ... + 22253.

It is an arithmetic number, because the mean of its divisors is an integer number (1697202).

Almost surely, 2^21540915 is an apocalyptic number.

21540915 is a deficient number, since it is larger than the sum of its proper divisors (19191933).

21540915 is a wasteful number, since it uses less digits than its factorization.

21540915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43539 (or 43536 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The square root of 21540915 is about 4641.2191286342. The cubic root of 21540915 is about 278.2411645371.

The spelling of 21540915 in words is "twenty-one million, five hundred forty thousand, nine hundred fifteen".