21609995 has 24 divisors (see below), whose sum is σ = 29762208. Its totient is φ = 15023360.

The previous prime is 21609977. The next prime is 21610003. The reversal of 21609995 is 59990612.

It is a de Polignac number, because none of the positive numbers 2^k-21609995 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13139 + ... + 14691.

It is an arithmetic number, because the mean of its divisors is an integer number (1240092).

Almost surely, 2^21609995 is an apocalyptic number.

21609995 is a deficient number, since it is larger than the sum of its proper divisors (8152213).

21609995 is a wasteful number, since it uses less digits than its factorization.

21609995 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1603 (or 1592 counting only the distinct ones).

The product of its (nonzero) digits is 43740, while the sum is 41.

The square root of 21609995 is about 4648.6551818779. The cubic root of 21609995 is about 278.5382795783.

It can be divided in two parts, 21 and 609995, that added together give a palindrome (610016).

The spelling of 21609995 in words is "twenty-one million, six hundred nine thousand, nine hundred ninety-five".