21135121031 has 4 divisors (see below), whose sum is σ = 21432798864. Its totient is φ = 20837443200.

The previous prime is 21135121001. The next prime is 21135121087. The reversal of 21135121031 is 13012153112.

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 21135121031 - 2⁶ = 21135120967 is a prime.

It is a super-2 number, since 2×21135121031² (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 = 21135120994 and 21135121012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135121001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 148838810 + ... + 148838951.

It is an arithmetic number, because the mean of its divisors is an integer number (5358199716).

Almost surely, 2^21135121031 is an apocalyptic number.

21135121031 is a deficient number, since it is larger than the sum of its proper divisors (297677833).

21135121031 is an equidigital number, since it uses as much as digits as its factorization.

21135121031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297677832.

The product of its (nonzero) digits is 180, while the sum is 20.

Adding to 21135121031 its reverse (13012153112), we get a palindrome (34147274143).

The spelling of 21135121031 in words is "twenty-one billion, one hundred thirty-five million, one hundred twenty-one thousand, thirty-one".