21540373 has 4 divisors (see below), whose sum is σ = 21697740. Its totient is φ = 21383008.

The previous prime is 21540367. The next prime is 21540383. The reversal of 21540373 is 37304512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 6932689 + 14607684 = 2633^2 + 3822^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540373 - 2⁵ = 21540341 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 (21540383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78478 + ... + 78751.

It is an arithmetic number, because the mean of its divisors is an integer number (5424435).

Almost surely, 2^21540373 is an apocalyptic number.

It is an amenable number.

21540373 is a deficient number, since it is larger than the sum of its proper divisors (157367).

21540373 is a wasteful number, since it uses less digits than its factorization.

21540373 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157366.

The product of its (nonzero) digits is 2520, while the sum is 25.

The square root of 21540373 is about 4641.1607384360. The cubic root of 21540373 is about 278.2388308700.

Adding to 21540373 its reverse (37304512), we get a palindrome (58844885).

The spelling of 21540373 in words is "twenty-one million, five hundred forty thousand, three hundred seventy-three".