21540667 has 4 divisors (see below), whose sum is σ = 21558456. Its totient is φ = 21522880.

The previous prime is 21540653. The next prime is 21540677. The reversal of 21540667 is 76604512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21540667 - 2²³ = 13152059 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21540637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6934 + ... + 9547.

It is an arithmetic number, because the mean of its divisors is an integer number (5389614).

Almost surely, 2^21540667 is an apocalyptic number.

21540667 is a deficient number, since it is larger than the sum of its proper divisors (17789).

21540667 is a wasteful number, since it uses less digits than its factorization.

21540667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17788.

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 21540667 is about 4641.1924114391. The cubic root of 21540667 is about 278.2400967385.

The spelling of 21540667 in words is "twenty-one million, five hundred forty thousand, six hundred sixty-seven".