21254765 has 16 divisors (see below), whose sum is σ = 29237760. Its totient is φ = 14530560.

The previous prime is 21254729. The next prime is 21254789. The reversal of 21254765 is 56745212.

It is not a de Polignac number, because 21254765 - 2¹⁶ = 21189229 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 14381 + ... + 15789.

It is an arithmetic number, because the mean of its divisors is an integer number (1827360).

Almost surely, 2^21254765 is an apocalyptic number.

It is an amenable number.

21254765 is a deficient number, since it is larger than the sum of its proper divisors (7982995).

21254765 is a wasteful number, since it uses less digits than its factorization.

21254765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1852.

The product of its digits is 16800, while the sum is 32.

The square root of 21254765 is about 4610.2890364922. The cubic root of 21254765 is about 277.0036144054.

Adding to 21254765 its reverse (56745212), we get a palindrome (77999977).

The spelling of 21254765 in words is "twenty-one million, two hundred fifty-four thousand, seven hundred sixty-five".