21121443251 has 8 divisors (see below), whose sum is σ = 21315150000. Its totient is φ = 20927855872.

The previous prime is 21121443227. The next prime is 21121443293. The reversal of 21121443251 is 15234412112.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121443251 is a prime.

It is a super-2 number, since 2×21121443251² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21121443251.

It is not an unprimeable number, because it can be changed into a prime (21121443151) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 347375 + ... + 403623.

It is an arithmetic number, because the mean of its divisors is an integer number (2664393750).

Almost surely, 2^21121443251 is an apocalyptic number.

21121443251 is a deficient number, since it is larger than the sum of its proper divisors (193706749).

21121443251 is a wasteful number, since it uses less digits than its factorization.

21121443251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59685.

The product of its digits is 1920, while the sum is 26.

Adding to 21121443251 its reverse (15234412112), we get a palindrome (36355855363).

The spelling of 21121443251 in words is "twenty-one billion, one hundred twenty-one million, four hundred forty-three thousand, two hundred fifty-one".