21405769 has 16 divisors (see below), whose sum is σ = 26956800. Its totient is φ = 16511760.

The previous prime is 21405749. The next prime is 21405773. The reversal of 21405769 is 96750412.

It is a cyclic number.

It is not a de Polignac number, because 21405769 - 2⁷ = 21405641 is a prime.

It is a super-2 number, since 2×21405769² = 916413892962722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21405749) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6582 + ... + 9280.

It is an arithmetic number, because the mean of its divisors is an integer number (1684800).

Almost surely, 2^21405769 is an apocalyptic number.

It is an amenable number.

21405769 is a deficient number, since it is larger than the sum of its proper divisors (5551031).

21405769 is a wasteful number, since it uses less digits than its factorization.

21405769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2820.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21405769 is about 4626.6368995200. The cubic root of 21405769 is about 277.6580556724.

The spelling of 21405769 in words is "twenty-one million, four hundred five thousand, seven hundred sixty-nine".