21220220172 has 24 divisors (see below), whose sum is σ = 49578932592. Its totient is φ = 7064108800.

The previous prime is 21220220159. The next prime is 21220220173. The reversal of 21220220172 is 27102202212.

It is not an unprimeable number, because it can be changed into a prime (21220220173) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1152729 + ... + 1170992.

It is an arithmetic number, because the mean of its divisors is an integer number (2065788858).

Almost surely, 2^21220220172 is an apocalyptic number.

It is an amenable number.

21220220172 is an abundant number, since it is smaller than the sum of its proper divisors (28358712420).

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

21220220172 is a wasteful number, since it uses less digits than its factorization.

21220220172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2324489 (or 2324487 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

Adding to 21220220172 its reverse (27102202212), we get a palindrome (48322422384).

The spelling of 21220220172 in words is "twenty-one billion, two hundred twenty million, two hundred twenty thousand, one hundred seventy-two".