21641605 has 8 divisors (see below), whose sum is σ = 26157600. Its totient is φ = 17188176.

The previous prime is 21641591. The next prime is 21641611. The reversal of 21641605 is 50614612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21641605 - 2⁹ = 21641093 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21641605.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14875 + ... + 16264.

It is an arithmetic number, because the mean of its divisors is an integer number (3269700).

Almost surely, 2^21641605 is an apocalyptic number.

It is an amenable number.

21641605 is a deficient number, since it is larger than the sum of its proper divisors (4515995).

21641605 is a wasteful number, since it uses less digits than its factorization.

21641605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31283.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21641605 is about 4652.0538474957. The cubic root of 21641605 is about 278.6740239492.

It can be divided in two parts, 216 and 41605, that multiplied together give a triangular number (8986680 = T₄₂₃₉).

The spelling of 21641605 in words is "twenty-one million, six hundred forty-one thousand, six hundred five".