21127557 has 8 divisors (see below), whose sum is σ = 30731040. Its totient is φ = 12804560.

The previous prime is 21127537. The next prime is 21127591. The reversal of 21127557 is 75572112.

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 21127557 - 2⁶ = 21127493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21127507) 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, 320082 + ... + 320147.

It is an arithmetic number, because the mean of its divisors is an integer number (3841380).

Almost surely, 2^21127557 is an apocalyptic number.

It is an amenable number.

21127557 is a deficient number, since it is larger than the sum of its proper divisors (9603483).

21127557 is a wasteful number, since it uses less digits than its factorization.

21127557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 640243.

The product of its digits is 4900, while the sum is 30.

The square root of 21127557 is about 4596.4722342249. The cubic root of 21127557 is about 276.4498937465.

Adding to 21127557 its reverse (75572112), we get a palindrome (96699669).

It can be divided in two parts, 2112 and 7557, that added together give a palindrome (9669).

The spelling of 21127557 in words is "twenty-one million, one hundred twenty-seven thousand, five hundred fifty-seven".