21540471 has 16 divisors (see below), whose sum is σ = 30518400. Its totient is φ = 13475808.

The previous prime is 21540439. The next prime is 21540473. The reversal of 21540471 is 17404512.

It is not a de Polignac number, because 21540471 - 2⁵ = 21540439 is a prime.

It is a super-3 number, since 3×21540471³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540473) 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, 4480 + ... + 7946.

It is an arithmetic number, because the mean of its divisors is an integer number (1907400).

Almost surely, 2^21540471 is an apocalyptic number.

21540471 is a deficient number, since it is larger than the sum of its proper divisors (8977929).

21540471 is a wasteful number, since it uses less digits than its factorization.

21540471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3598.

The product of its (nonzero) digits is 1120, while the sum is 24.

The square root of 21540471 is about 4641.1712961277. The cubic root of 21540471 is about 278.2392528274.

Adding to 21540471 its reverse (17404512), we get a palindrome (38944983).

The spelling of 21540471 in words is "twenty-one million, five hundred forty thousand, four hundred seventy-one".