21540993 has 16 divisors (see below), whose sum is σ = 30132480. Its totient is φ = 13671936.

The previous prime is 21540983. The next prime is 21541019. The reversal of 21540993 is 39904512.

It is not a de Polignac number, because 21540993 - 2¹² = 21536897 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21540983) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3153 + ... + 7281.

It is an arithmetic number, because the mean of its divisors is an integer number (1883280).

Almost surely, 2^21540993 is an apocalyptic number.

It is an amenable number.

21540993 is a deficient number, since it is larger than the sum of its proper divisors (8591487).

21540993 is a wasteful number, since it uses less digits than its factorization.

21540993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4216.

The product of its (nonzero) digits is 9720, while the sum is 33.

The square root of 21540993 is about 4641.2275315912. The cubic root of 21540993 is about 278.2415003753.

The spelling of 21540993 in words is "twenty-one million, five hundred forty thousand, nine hundred ninety-three".