21385665 has 24 divisors (see below), whose sum is σ = 42364608. Its totient is φ = 9776160.

The previous prime is 21385649. The next prime is 21385681. The reversal of 21385665 is 56658312.

It is an interprime number because it is at equal distance from previous prime (21385649) and next prime (21385681).

It is not a de Polignac number, because 21385665 - 2⁴ = 21385649 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33631 + ... + 34260.

It is an arithmetic number, because the mean of its divisors is an integer number (1765192).

Almost surely, 2^21385665 is an apocalyptic number.

It is an amenable number.

21385665 is a deficient number, since it is larger than the sum of its proper divisors (20978943).

21385665 is a wasteful number, since it uses less digits than its factorization.

21385665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67909 (or 67906 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 21385665 is about 4624.4637526961. The cubic root of 21385665 is about 277.5711042531.

The spelling of 21385665 in words is "twenty-one million, three hundred eighty-five thousand, six hundred sixty-five".