21609423 has 40 divisors (see below), whose sum is σ = 35777280. Its totient is φ = 12888720.

The previous prime is 21609407. The next prime is 21609439. The reversal of 21609423 is 32490612.

It is an interprime number because it is at equal distance from previous prime (21609407) and next prime (21609439).

It is not a de Polignac number, because 21609423 - 2⁴ = 21609407 is a prime.

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

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21609473) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 70236 + ... + 70542.

It is an arithmetic number, because the mean of its divisors is an integer number (894432).

Almost surely, 2^21609423 is an apocalyptic number.

21609423 is a deficient number, since it is larger than the sum of its proper divisors (14167857).

21609423 is a wasteful number, since it uses less digits than its factorization.

21609423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 409 (or 400 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21609423 is about 4648.5936583014. The cubic root of 21609423 is about 278.5358219917.

The spelling of 21609423 in words is "twenty-one million, six hundred nine thousand, four hundred twenty-three".