21078017 has 4 divisors (see below), whose sum is σ = 21098496. Its totient is φ = 21057540.

The previous prime is 21077971. The next prime is 21078053. The reversal of 21078017 is 71087012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21078017 - 2²⁴ = 4300801 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21078067) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8609 + ... + 10782.

It is an arithmetic number, because the mean of its divisors is an integer number (5274624).

It is a Proth number, since it is equal to 2573 ⋅ 2¹³ + 1 and 2573 < 2¹³.

Almost surely, 2^21078017 is an apocalyptic number.

It is an amenable number.

21078017 is a deficient number, since it is larger than the sum of its proper divisors (20479).

21078017 is a wasteful number, since it uses less digits than its factorization.

21078017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20478.

The product of its (nonzero) digits is 784, while the sum is 26.

The square root of 21078017 is about 4591.0801561288. The cubic root of 21078017 is about 276.2336509506.

The spelling of 21078017 in words is "twenty-one million, seventy-eight thousand, seventeen".