21065775 has 24 divisors (see below), whose sum is σ = 36664320. Its totient is φ = 10643040.

The previous prime is 21065767. The next prime is 21065777. The reversal of 21065775 is 57756012.

It is not a de Polignac number, because 21065775 - 2³ = 21065767 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065777) 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 23 ways as a sum of consecutive naturals, for example, 5967 + ... + 8816.

It is an arithmetic number, because the mean of its divisors is an integer number (1527680).

Almost surely, 2^21065775 is an apocalyptic number.

21065775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21065775 is a deficient number, since it is larger than the sum of its proper divisors (15598545).

21065775 is a wasteful number, since it uses less digits than its factorization.

21065775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14815 (or 14810 counting only the distinct ones).

The product of its (nonzero) digits is 14700, while the sum is 33.

The square root of 21065775 is about 4589.7467250383. The cubic root of 21065775 is about 276.1801622496.

The spelling of 21065775 in words is "twenty-one million, sixty-five thousand, seven hundred seventy-five".