21305079 has 8 divisors (see below), whose sum is σ = 31563120. Its totient is φ = 14203368.

The previous prime is 21305071. The next prime is 21305101. The reversal of 21305079 is 97050312.

It is not a de Polignac number, because 21305079 - 2³ = 21305071 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 789077 = 21305079 / (2 + 1 + 3 + 0 + 5 + 0 + 7 + 9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305071) 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, 394512 + ... + 394565.

It is an arithmetic number, because the mean of its divisors is an integer number (3945390).

Almost surely, 2^21305079 is an apocalyptic number.

21305079 is a deficient number, since it is larger than the sum of its proper divisors (10258041).

21305079 is an equidigital number, since it uses as much as digits as its factorization.

21305079 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 789086 (or 789080 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21305079 is about 4615.7425188154. The cubic root of 21305079 is about 277.2220152677. Note that the first 3 decimals are identical.

The spelling of 21305079 in words is "twenty-one million, three hundred five thousand, seventy-nine".