21152212221 has 8 divisors (see below), whose sum is σ = 32231942464. Its totient is φ = 12086978400.

The previous prime is 21152212069. The next prime is 21152212303. The reversal of 21152212221 is 12221225112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21152212221 - 2¹⁹ = 21151687933 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1007248201 = 21152212221 / (2 + 1 + 1 + 5 + 2 + 2 + 1 + 2 + 2 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21152212321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 503624080 + ... + 503624121.

It is an arithmetic number, because the mean of its divisors is an integer number (4028992808).

Almost surely, 2^21152212221 is an apocalyptic number.

21152212221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21152212221 is a deficient number, since it is larger than the sum of its proper divisors (11079730243).

21152212221 is a wasteful number, since it uses less digits than its factorization.

21152212221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1007248211.

The product of its digits is 320, while the sum is 21.

Adding to 21152212221 its reverse (12221225112), we get a palindrome (33373437333).

The spelling of 21152212221 in words is "twenty-one billion, one hundred fifty-two million, two hundred twelve thousand, two hundred twenty-one".