21078961 has 8 divisors (see below), whose sum is σ = 22730400. Its totient is φ = 19481760.

The previous prime is 21078949. The next prime is 21078991. The reversal of 21078961 is 16987012.

It is a happy number.

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 21078961 - 2¹⁹ = 20554673 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21078931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12751 + ... + 14308.

It is an arithmetic number, because the mean of its divisors is an integer number (2841300).

Almost surely, 2^21078961 is an apocalyptic number.

It is an amenable number.

21078961 is a deficient number, since it is larger than the sum of its proper divisors (1651439).

21078961 is a wasteful number, since it uses less digits than its factorization.

21078961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27119.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21078961 is about 4591.1829630282. The cubic root of 21078961 is about 276.2377746888.

The spelling of 21078961 in words is "twenty-one million, seventy-eight thousand, nine hundred sixty-one".