21078965 has 8 divisors (see below), whose sum is σ = 25527480. Its totient is φ = 16708032.

The previous prime is 21078949. The next prime is 21078991. The reversal of 21078965 is 56987012.

It can be written as a sum of positive squares in 4 ways, for example, as 303601 + 20775364 = 551^2 + 4558^2 .

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 21078965 - 2⁴ = 21078949 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18794 + ... + 19883.

It is an arithmetic number, because the mean of its divisors is an integer number (3190935).

Almost surely, 2^21078965 is an apocalyptic number.

It is an amenable number.

21078965 is a deficient number, since it is larger than the sum of its proper divisors (4448515).

21078965 is a wasteful number, since it uses less digits than its factorization.

21078965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38791.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 21078965 is about 4591.1833986457. The cubic root of 21078965 is about 276.2377921620.

The spelling of 21078965 in words is "twenty-one million, seventy-eight thousand, nine hundred sixty-five".