21385791 has 24 divisors (see below), whose sum is σ = 36840960. Its totient is φ = 11688336.

The previous prime is 21385783. The next prime is 21385801. The reversal of 21385791 is 19758312.

It is not a de Polignac number, because 21385791 - 2³ = 21385783 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385781) by changing a digit.

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, 5931 + ... + 8828.

It is an arithmetic number, because the mean of its divisors is an integer number (1535040).

Almost surely, 2^21385791 is an apocalyptic number.

21385791 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21385791 is a deficient number, since it is larger than the sum of its proper divisors (15455169).

21385791 is a wasteful number, since it uses less digits than its factorization.

21385791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14795 (or 14792 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21385791 is about 4624.4773758772. The cubic root of 21385791 is about 277.5716493829.

The spelling of 21385791 in words is "twenty-one million, three hundred eighty-five thousand, seven hundred ninety-one".