21085757 has 16 divisors (see below), whose sum is σ = 26417664. Its totient is φ = 16350000.

The previous prime is 21085747. The next prime is 21085769. The reversal of 21085757 is 75758012.

It is a cyclic number.

It is not a de Polignac number, because 21085757 - 2¹⁰ = 21084733 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085717) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18782 + ... + 19872.

It is an arithmetic number, because the mean of its divisors is an integer number (1651104).

Almost surely, 2^21085757 is an apocalyptic number.

It is an amenable number.

21085757 is a deficient number, since it is larger than the sum of its proper divisors (5331907).

21085757 is a wasteful number, since it uses less digits than its factorization.

21085757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1360.

The product of its (nonzero) digits is 19600, while the sum is 35.

The square root of 21085757 is about 4591.9230176474. The cubic root of 21085757 is about 276.2674584764.

The spelling of 21085757 in words is "twenty-one million, eighty-five thousand, seven hundred fifty-seven".