21209486 has 4 divisors (see below), whose sum is σ = 31814232. Its totient is φ = 10604742.

The previous prime is 21209471. The next prime is 21209537. The reversal of 21209486 is 68490212.

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

It is a super-5 number, since 5×21209486⁵ (a number of 38 digits) contains 55555 as substring.

It is a congruent number.

It is an unprimeable number.

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, 5302370 + ... + 5302373.

It is an arithmetic number, because the mean of its divisors is an integer number (7953558).

Almost surely, 2^21209486 is an apocalyptic number.

21209486 is a deficient number, since it is larger than the sum of its proper divisors (10604746).

21209486 is a wasteful number, since it uses less digits than its factorization.

21209486 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10604745.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21209486 is about 4605.3757718562. The cubic root of 21209486 is about 276.8067744090.

Adding to 21209486 its reverse (68490212), we get a palindrome (89699698).

The spelling of 21209486 in words is "twenty-one million, two hundred nine thousand, four hundred eighty-six".