21121553531 has 8 divisors (see below), whose sum is σ = 22767038784. Its totient is φ = 19479032640.

The previous prime is 21121553507. The next prime is 21121553543. The reversal of 21121553531 is 13535512112.

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-21121553531 is a prime.

It is a super-2 number, since 2×21121553531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121553494 and 21121553503.

It is not an unprimeable number, because it can be changed into a prime (21121553501) 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, 726275 + ... + 754796.

It is an arithmetic number, because the mean of its divisors is an integer number (2845879848).

Almost surely, 2^21121553531 is an apocalyptic number.

21121553531 is a deficient number, since it is larger than the sum of its proper divisors (1645485253).

21121553531 is a wasteful number, since it uses less digits than its factorization.

21121553531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1482181.

The product of its digits is 4500, while the sum is 29.

The spelling of 21121553531 in words is "twenty-one billion, one hundred twenty-one million, five hundred fifty-three thousand, five hundred thirty-one".