21676665 has 16 divisors (see below), whose sum is σ = 34823808. Its totient is φ = 11513856.

The previous prime is 21676661. The next prime is 21676667. The reversal of 21676665 is 56667612.

It is not a de Polignac number, because 21676665 - 2² = 21676661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21676661) 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, 1044 + ... + 6666.

It is an arithmetic number, because the mean of its divisors is an integer number (2176488).

Almost surely, 2^21676665 is an apocalyptic number.

It is an amenable number.

21676665 is a deficient number, since it is larger than the sum of its proper divisors (13147143).

21676665 is a wasteful number, since it uses less digits than its factorization.

21676665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5888.

The product of its digits is 90720, while the sum is 39.

The square root of 21676665 is about 4655.8205506656. The cubic root of 21676665 is about 278.8244293060.

The spelling of 21676665 in words is "twenty-one million, six hundred seventy-six thousand, six hundred sixty-five".