21609459 has 12 divisors (see below), whose sum is σ = 31422352. Its totient is φ = 14310000.

The previous prime is 21609439. The next prime is 21609461. The reversal of 21609459 is 95490612.

21609459 is a `hidden beast` number, since 2 + 1 + 609 + 45 + 9 = 666.

It is not a de Polignac number, because 21609459 - 2¹⁶ = 21543923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21609439) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6592 + ... + 9309.

Almost surely, 2^21609459 is an apocalyptic number.

21609459 is a deficient number, since it is larger than the sum of its proper divisors (9812893).

21609459 is a wasteful number, since it uses less digits than its factorization.

21609459 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16058 (or 16055 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 21609459 is about 4648.5975304386. The cubic root of 21609459 is about 278.5359766663.

It can be divided in two parts, 216094 and 59, that added together give a triangular number (216153 = T₆₅₇).

The spelling of 21609459 in words is "twenty-one million, six hundred nine thousand, four hundred fifty-nine".