21090975 has 24 divisors (see below), whose sum is σ = 36076560. Its totient is φ = 10859520.

The previous prime is 21090967. The next prime is 21091003. The reversal of 21090975 is 57909012.

It is not a de Polignac number, because 21090975 - 2³ = 21090967 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2674 + ... + 7023.

It is an arithmetic number, because the mean of its divisors is an integer number (1503190).

Almost surely, 2^21090975 is an apocalyptic number.

21090975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21090975 is a deficient number, since it is larger than the sum of its proper divisors (14985585).

21090975 is a wasteful number, since it uses less digits than its factorization.

21090975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9739 (or 9734 counting only the distinct ones).

The product of its (nonzero) digits is 5670, while the sum is 33.

The square root of 21090975 is about 4592.4911540470. The cubic root of 21090975 is about 276.2902454964.

Adding to 21090975 its reverse (57909012), we get a palindrome (78999987).

The spelling of 21090975 in words is "twenty-one million, ninety thousand, nine hundred seventy-five".