21106031 has 4 divisors (see below), whose sum is σ = 21504312. Its totient is φ = 20707752.

The previous prime is 21105977. The next prime is 21106037. The reversal of 21106031 is 13060112.

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 21106031 - 2⁶ = 21105967 is a prime.

It is a super-2 number, since 2×21106031² = 890929089145922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21105997 and 21106015.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21106037) 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, 199061 + ... + 199166.

It is an arithmetic number, because the mean of its divisors is an integer number (5376078).

Almost surely, 2^21106031 is an apocalyptic number.

21106031 is a deficient number, since it is larger than the sum of its proper divisors (398281).

21106031 is an equidigital number, since it uses as much as digits as its factorization.

21106031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398280.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 21106031 is about 4594.1300591080. The cubic root of 21106031 is about 276.3559740285.

Adding to 21106031 its reverse (13060112), we get a palindrome (34166143).

The spelling of 21106031 in words is "twenty-one million, one hundred six thousand, thirty-one".