21121210172 has 12 divisors (see below), whose sum is σ = 37244272296. Its totient is φ = 10479989520.

The previous prime is 21121210171. The next prime is 21121210237. The reversal of 21121210172 is 27101212112.

It is a happy number.

It is a super-2 number, since 2×21121210172² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121210171) 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 3 ways as a sum of consecutive naturals, for example, 20153303 + ... + 20154350.

It is an arithmetic number, because the mean of its divisors is an integer number (3103689358).

Almost surely, 2^21121210172 is an apocalyptic number.

It is an amenable number.

21121210172 is a deficient number, since it is larger than the sum of its proper divisors (16123062124).

21121210172 is a wasteful number, since it uses less digits than its factorization.

21121210172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40307788 (or 40307786 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 20.

Adding to 21121210172 its reverse (27101212112), we get a palindrome (48222422284).

The spelling of 21121210172 in words is "twenty-one billion, one hundred twenty-one million, two hundred ten thousand, one hundred seventy-two".