21540775 has 24 divisors (see below), whose sum is σ = 28458000. Its totient is φ = 16128000.

The previous prime is 21540773. The next prime is 21540787. The reversal of 21540775 is 57704512.

It is not a de Polignac number, because 21540775 - 2¹ = 21540773 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540773) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 47751 + ... + 48199.

It is an arithmetic number, because the mean of its divisors is an integer number (1185750).

Almost surely, 2^21540775 is an apocalyptic number.

21540775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21540775 is a deficient number, since it is larger than the sum of its proper divisors (6917225).

21540775 is a wasteful number, since it uses less digits than its factorization.

21540775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 579 (or 574 counting only the distinct ones).

The product of its (nonzero) digits is 9800, while the sum is 31.

The square root of 21540775 is about 4641.2040463656. The cubic root of 21540775 is about 278.2405617486.

The spelling of 21540775 in words is "twenty-one million, five hundred forty thousand, seven hundred seventy-five".