21505006 has 4 divisors (see below), whose sum is σ = 32257512. Its totient is φ = 10752502.

The previous prime is 21504971. The next prime is 21505007. The reversal of 21505006 is 60050512.

It is a happy number.

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 (21505007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5376250 + ... + 5376253.

It is an arithmetic number, because the mean of its divisors is an integer number (8064378).

Almost surely, 2^21505006 is an apocalyptic number.

21505006 is a deficient number, since it is larger than the sum of its proper divisors (10752506).

21505006 is a wasteful number, since it uses less digits than its factorization.

21505006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10752505.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21505006 is about 4637.3490271922. The cubic root of 21505006 is about 278.0864679355.

Adding to 21505006 its reverse (60050512), we get a palindrome (81555518).

The spelling of 21505006 in words is "twenty-one million, five hundred five thousand, six".