21540851 has 16 divisors (see below), whose sum is σ = 23347200. Its totient is φ = 19813248.

The previous prime is 21540847. The next prime is 21540859. The reversal of 21540851 is 15804512.

It is a cyclic number.

It is not a de Polignac number, because 21540851 - 2² = 21540847 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21540851.

It is not an unprimeable number, because it can be changed into a prime (21540859) 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, 169550 + ... + 169676.

It is an arithmetic number, because the mean of its divisors is an integer number (1459200).

Almost surely, 2^21540851 is an apocalyptic number.

21540851 is a deficient number, since it is larger than the sum of its proper divisors (1806349).

21540851 is a wasteful number, since it uses less digits than its factorization.

21540851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 338.

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 21540851 is about 4641.2122338889. The cubic root of 21540851 is about 278.2408889770.

The spelling of 21540851 in words is "twenty-one million, five hundred forty thousand, eight hundred fifty-one".