21517966 has 4 divisors (see below), whose sum is σ = 32276952. Its totient is φ = 10758982.

The previous prime is 21517961. The next prime is 21517967. The reversal of 21517966 is 66971512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21517961) 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 as a sum of consecutive naturals, namely, 5379490 + ... + 5379493.

It is an arithmetic number, because the mean of its divisors is an integer number (8069238).

Almost surely, 2^21517966 is an apocalyptic number.

21517966 is a deficient number, since it is larger than the sum of its proper divisors (10758986).

21517966 is a wasteful number, since it uses less digits than its factorization.

21517966 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10758985.

The product of its digits is 22680, while the sum is 37.

The square root of 21517966 is about 4638.7461667998. The cubic root of 21517966 is about 278.1423196890.

It can be divided in two parts, 215 and 17966, that added together give a palindrome (18181).

The spelling of 21517966 in words is "twenty-one million, five hundred seventeen thousand, nine hundred sixty-six".