21540007 has 4 divisors (see below), whose sum is σ = 21573256. Its totient is φ = 21506760.

The previous prime is 21539993. The next prime is 21540017. The reversal of 21540007 is 70004512.

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 21540007 - 2⁷ = 21539879 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540017) 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, 15633 + ... + 16954.

It is an arithmetic number, because the mean of its divisors is an integer number (5393314).

Almost surely, 2^21540007 is an apocalyptic number.

21540007 is a deficient number, since it is larger than the sum of its proper divisors (33249).

21540007 is an equidigital number, since it uses as much as digits as its factorization.

21540007 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33248.

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 21540007 is about 4641.1213084771. The cubic root of 21540007 is about 278.2372549767.

Adding to 21540007 its reverse (70004512), we get a palindrome (91544519).

The spelling of 21540007 in words is "twenty-one million, five hundred forty thousand, seven".