21220506 has 24 divisors (see below), whose sum is σ = 46562880. Its totient is φ = 6983496.

The previous prime is 21220501. The next prime is 21220531. The reversal of 21220506 is 60502212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21220501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6040 + ... + 8883.

It is an arithmetic number, because the mean of its divisors is an integer number (1940120).

Almost surely, 2^21220506 is an apocalyptic number.

21220506 is an abundant number, since it is smaller than the sum of its proper divisors (25342374).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21220506 is a wasteful number, since it uses less digits than its factorization.

21220506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15010 (or 15007 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21220506 is about 4606.5720443731. The cubic root of 21220506 is about 276.8547070887.

Adding to 21220506 its reverse (60502212), we get a palindrome (81722718).

The spelling of 21220506 in words is "twenty-one million, two hundred twenty thousand, five hundred six".