21121145551 has 4 divisors (see below), whose sum is σ = 23041249704. Its totient is φ = 19201041400.

The previous prime is 21121145489. The next prime is 21121145557. The reversal of 21121145551 is 15554112112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21121145551 - 2²¹ = 21119048399 is a prime.

It is a super-2 number, since 2×21121145551² (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 (21121145557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 960052060 + ... + 960052081.

It is an arithmetic number, because the mean of its divisors is an integer number (5760312426).

Almost surely, 2^21121145551 is an apocalyptic number.

21121145551 is a deficient number, since it is larger than the sum of its proper divisors (1920104153).

21121145551 is a wasteful number, since it uses less digits than its factorization.

21121145551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1920104152.

The product of its digits is 2000, while the sum is 28.

Adding to 21121145551 its reverse (15554112112), we get a palindrome (36675257663).

The spelling of 21121145551 in words is "twenty-one billion, one hundred twenty-one million, one hundred forty-five thousand, five hundred fifty-one".