21129577 has 16 divisors (see below), whose sum is σ = 25753600. Its totient is φ = 16932240.

The previous prime is 21129557. The next prime is 21129583. The reversal of 21129577 is 77592112.

It is a cyclic number.

It is not a de Polignac number, because 21129577 - 2¹⁹ = 20605289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21129547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9502 + ... + 11512.

It is an arithmetic number, because the mean of its divisors is an integer number (1609600).

Almost surely, 2^21129577 is an apocalyptic number.

It is an amenable number.

21129577 is a deficient number, since it is larger than the sum of its proper divisors (4624023).

21129577 is a wasteful number, since it uses less digits than its factorization.

21129577 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2116.

The product of its digits is 8820, while the sum is 34.

The square root of 21129577 is about 4596.6919627054. The cubic root of 21129577 is about 276.4587038989.

The spelling of 21129577 in words is "twenty-one million, one hundred twenty-nine thousand, five hundred seventy-seven".