21769409 has 4 divisors (see below), whose sum is σ = 22471680. Its totient is φ = 21067140.

The previous prime is 21769393. The next prime is 21769411. The reversal of 21769409 is 90496712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21769409 - 2⁴ = 21769393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21769499) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 351089 + ... + 351150.

It is an arithmetic number, because the mean of its divisors is an integer number (5617920).

Almost surely, 2^21769409 is an apocalyptic number.

It is an amenable number.

21769409 is a deficient number, since it is larger than the sum of its proper divisors (702271).

21769409 is an equidigital number, since it uses as much as digits as its factorization.

21769409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 702270.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 21769409 is about 4665.7699257464. The cubic root of 21769409 is about 279.2215153041.

The spelling of 21769409 in words is "twenty-one million, seven hundred sixty-nine thousand, four hundred nine".