21540387 has 8 divisors (see below), whose sum is σ = 31331520. Its totient is φ = 13054760.

The previous prime is 21540383. The next prime is 21540437. The reversal of 21540387 is 78304512.

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

It is a cyclic number.

It is not a de Polignac number, because 21540387 - 2² = 21540383 is a prime.

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 7 ways as a sum of consecutive naturals, for example, 326337 + ... + 326402.

It is an arithmetic number, because the mean of its divisors is an integer number (3916440).

Almost surely, 2^21540387 is an apocalyptic number.

21540387 is a deficient number, since it is larger than the sum of its proper divisors (9791133).

21540387 is a wasteful number, since it uses less digits than its factorization.

21540387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 652753.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 21540387 is about 4641.1622466792. The cubic root of 21540387 is about 278.2388911497.

Adding to 21540387 its reverse (78304512), we get a palindrome (99844899).

The spelling of 21540387 in words is "twenty-one million, five hundred forty thousand, three hundred eighty-seven".