21115947 has 16 divisors (see below), whose sum is σ = 28748160. Its totient is φ = 13783872.

The previous prime is 21115933. The next prime is 21115949. The reversal of 21115947 is 74951112.

It is not a de Polignac number, because 21115947 - 2⁴ = 21115931 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21115949) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33804 + ... + 34422.

It is an arithmetic number, because the mean of its divisors is an integer number (1796760).

Almost surely, 2^21115947 is an apocalyptic number.

21115947 is a deficient number, since it is larger than the sum of its proper divisors (7632213).

21115947 is a wasteful number, since it uses less digits than its factorization.

21115947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 842.

The product of its digits is 2520, while the sum is 30.

The square root of 21115947 is about 4595.2091356107. The cubic root of 21115947 is about 276.3992462856.

The spelling of 21115947 in words is "twenty-one million, one hundred fifteen thousand, nine hundred forty-seven".