21021123031 has 4 divisors (see below), whose sum is σ = 21229253064. Its totient is φ = 20812993000.

The previous prime is 21021123023. The next prime is 21021123041. The reversal of 21021123031 is 13032112012.

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 21021123031 - 2³ = 21021123023 is a prime.

It is a super-2 number, since 2×21021123031² (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 = 21021122996 and 21021123014.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021123041) 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, 104064865 + ... + 104065066.

It is an arithmetic number, because the mean of its divisors is an integer number (5307313266).

Almost surely, 2^21021123031 is an apocalyptic number.

21021123031 is a deficient number, since it is larger than the sum of its proper divisors (208130033).

21021123031 is a wasteful number, since it uses less digits than its factorization.

21021123031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208130032.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21021123031 its reverse (13032112012), we get a palindrome (34053235043).

The spelling of 21021123031 in words is "twenty-one billion, twenty-one million, one hundred twenty-three thousand, thirty-one".