21540751 has 4 divisors (see below), whose sum is σ = 22807872. Its totient is φ = 20273632.

The previous prime is 21540731. The next prime is 21540763. The reversal of 21540751 is 15704512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21540751 - 2¹¹ = 21538703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 633535 + ... + 633568.

It is an arithmetic number, because the mean of its divisors is an integer number (5701968).

Almost surely, 2^21540751 is an apocalyptic number.

21540751 is a deficient number, since it is larger than the sum of its proper divisors (1267121).

21540751 is a wasteful number, since it uses less digits than its factorization.

21540751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1267120.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21540751 is about 4641.2014608289. The cubic root of 21540751 is about 278.2404584132.

The spelling of 21540751 in words is "twenty-one million, five hundred forty thousand, seven hundred fifty-one".