21097405 has 16 divisors (see below), whose sum is σ = 29018880. Its totient is φ = 14424192.

The previous prime is 21097393. The next prime is 21097421. The reversal of 21097405 is 50479012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21097405 - 2¹¹ = 21095357 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15336 + ... + 16654.

It is an arithmetic number, because the mean of its divisors is an integer number (1813680).

Almost surely, 2^21097405 is an apocalyptic number.

It is an amenable number.

21097405 is a deficient number, since it is larger than the sum of its proper divisors (7921475).

21097405 is a wasteful number, since it uses less digits than its factorization.

21097405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1788.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21097405 is about 4593.1911564837. The cubic root of 21097405 is about 276.3183201550.

The spelling of 21097405 in words is "twenty-one million, ninety-seven thousand, four hundred five".