21078061 has 4 divisors (see below), whose sum is σ = 21088672. Its totient is φ = 21067452.

The previous prime is 21078053. The next prime is 21078067. The reversal of 21078061 is 16087012.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21078061 - 2³ = 21078053 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 1335 + ... + 6628.

It is an arithmetic number, because the mean of its divisors is an integer number (5272168).

Almost surely, 2^21078061 is an apocalyptic number.

It is an amenable number.

21078061 is a deficient number, since it is larger than the sum of its proper divisors (10611).

21078061 is an equidigital number, since it uses as much as digits as its factorization.

21078061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10610.

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 21078061 is about 4591.0849480270. The cubic root of 21078061 is about 276.2338431615.

The spelling of 21078061 in words is "twenty-one million, seventy-eight thousand, sixty-one".