21138757 has 8 divisors (see below), whose sum is σ = 21987680. Its totient is φ = 20306160.

The previous prime is 21138751. The next prime is 21138781. The reversal of 21138757 is 75783112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21138757 - 2¹⁹ = 20614469 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138751) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1407 + ... + 6652.

It is an arithmetic number, because the mean of its divisors is an integer number (2748460).

Almost surely, 2^21138757 is an apocalyptic number.

It is an amenable number.

21138757 is a deficient number, since it is larger than the sum of its proper divisors (848923).

21138757 is an equidigital number, since it uses as much as digits as its factorization.

21138757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8163.

The product of its digits is 11760, while the sum is 34.

The square root of 21138757 is about 4597.6903984501. The cubic root of 21138757 is about 276.4987350434.

The spelling of 21138757 in words is "twenty-one million, one hundred thirty-eight thousand, seven hundred fifty-seven".