21392505 has 28 divisors (see below), whose sum is σ = 38495460. Its totient is φ = 11407392.

The previous prime is 21392491. The next prime is 21392509. The reversal of 21392505 is 50529312.

It can be written as a sum of positive squares in 2 ways, for example, as 4549689 + 16842816 = 2133^2 + 4104^2 .

It is not a de Polignac number, because 21392505 - 2¹⁰ = 21391481 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21392509) 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 27 ways as a sum of consecutive naturals, for example, 711 + ... + 6579.

Almost surely, 2^21392505 is an apocalyptic number.

It is an amenable number.

21392505 is a deficient number, since it is larger than the sum of its proper divisors (17102955).

21392505 is an frugal number, since it uses more digits than its factorization.

21392505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5892 (or 5877 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 27.

The square root of 21392505 is about 4625.2032387777. The cubic root of 21392505 is about 277.6006939179.

The spelling of 21392505 in words is "twenty-one million, three hundred ninety-two thousand, five hundred five".