21620247 has 16 divisors (see below), whose sum is σ = 32299392. Its totient is φ = 12748320.

The previous prime is 21620239. The next prime is 21620251. The reversal of 21620247 is 74202612.

It is not a de Polignac number, because 21620247 - 2³ = 21620239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7633 + ... + 10074.

It is an arithmetic number, because the mean of its divisors is an integer number (2018712).

Almost surely, 2^21620247 is an apocalyptic number.

21620247 is a deficient number, since it is larger than the sum of its proper divisors (10679145).

21620247 is a wasteful number, since it uses less digits than its factorization.

21620247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17758.

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 21620247 is about 4649.7577356245. The cubic root of 21620247 is about 278.5823197395.

Adding to 21620247 its reverse (74202612), we get a palindrome (95822859).

The spelling of 21620247 in words is "twenty-one million, six hundred twenty thousand, two hundred forty-seven".