21379947 has 4 divisors (see below), whose sum is σ = 28506600. Its totient is φ = 14253296.

The previous prime is 21379933. The next prime is 21379957. The reversal of 21379947 is 74997312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21379947 - 2¹⁰ = 21378923 is a prime.

It is a super-3 number, since 3×21379947³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21379899 and 21379908.

It is not an unprimeable number, because it can be changed into a prime (21379907) 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, 3563322 + ... + 3563327.

It is an arithmetic number, because the mean of its divisors is an integer number (7126650).

Almost surely, 2^21379947 is an apocalyptic number.

21379947 is a deficient number, since it is larger than the sum of its proper divisors (7126653).

21379947 is an equidigital number, since it uses as much as digits as its factorization.

21379947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7126652.

The product of its digits is 95256, while the sum is 42.

The square root of 21379947 is about 4623.8454775219. The cubic root of 21379947 is about 277.5463634895.

The spelling of 21379947 in words is "twenty-one million, three hundred seventy-nine thousand, nine hundred forty-seven".