21605419 has 16 divisors (see below), whose sum is σ = 25767936. Its totient is φ = 17884800.

The previous prime is 21605417. The next prime is 21605429. The reversal of 21605419 is 91450612.

It is a cyclic number.

It is not a de Polignac number, because 21605419 - 2¹ = 21605417 is a prime.

It is a super-2 number, since 2×21605419² = 933588260331122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21605411) 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, 3934 + ... + 7660.

It is an arithmetic number, because the mean of its divisors is an integer number (1610496).

Almost surely, 2^21605419 is an apocalyptic number.

21605419 is a deficient number, since it is larger than the sum of its proper divisors (4162517).

21605419 is a wasteful number, since it uses less digits than its factorization.

21605419 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3786.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21605419 is about 4648.1629704648. The cubic root of 21605419 is about 278.5186176712.

The spelling of 21605419 in words is "twenty-one million, six hundred five thousand, four hundred nineteen".