21540406 has 8 divisors (see below), whose sum is σ = 32765904. Its totient is φ = 10618440.

The previous prime is 21540383. The next prime is 21540437. The reversal of 21540406 is 60404512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75705 + ... + 75988.

It is an arithmetic number, because the mean of its divisors is an integer number (4095738).

Almost surely, 2^21540406 is an apocalyptic number.

21540406 is a deficient number, since it is larger than the sum of its proper divisors (11225498).

21540406 is a wasteful number, since it uses less digits than its factorization.

21540406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151766.

The product of its (nonzero) digits is 960, while the sum is 22.

The square root of 21540406 is about 4641.1642935798. The cubic root of 21540406 is about 278.2389729578.

Adding to 21540406 its reverse (60404512), we get a palindrome (81944918).

The spelling of 21540406 in words is "twenty-one million, five hundred forty thousand, four hundred six".