21649965 has 8 divisors (see below), whose sum is σ = 34639968. Its totient is φ = 11546640.

The previous prime is 21649963. The next prime is 21649967. The reversal of 21649965 is 56994612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21649963) and next prime (21649967).

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

It is not a de Polignac number, because 21649965 - 2¹ = 21649963 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21649961) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 721651 + ... + 721680.

It is an arithmetic number, because the mean of its divisors is an integer number (4329996).

Almost surely, 2^21649965 is an apocalyptic number.

It is an amenable number.

21649965 is a deficient number, since it is larger than the sum of its proper divisors (12990003).

21649965 is a wasteful number, since it uses less digits than its factorization.

21649965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1443339.

The product of its digits is 116640, while the sum is 42.

The square root of 21649965 is about 4652.9522886013. The cubic root of 21649965 is about 278.7099026024.

The spelling of 21649965 in words is "twenty-one million, six hundred forty-nine thousand, nine hundred sixty-five".