21106731 has 4 divisors (see below), whose sum is σ = 28142312. Its totient is φ = 14071152.

The previous prime is 21106721. The next prime is 21106763. The reversal of 21106731 is 13760112.

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

It is not a de Polignac number, because 21106731 - 2⁹ = 21106219 is a prime.

It is a super-2 number, since 2×21106731² = 890988187012722, 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 = 21106698 and 21106707.

It is not an unprimeable number, because it can be changed into a prime (21106721) 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, 3517786 + ... + 3517791.

It is an arithmetic number, because the mean of its divisors is an integer number (7035578).

Almost surely, 2^21106731 is an apocalyptic number.

21106731 is a deficient number, since it is larger than the sum of its proper divisors (7035581).

21106731 is an equidigital number, since it uses as much as digits as its factorization.

21106731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7035580.

The product of its (nonzero) digits is 252, while the sum is 21.

The square root of 21106731 is about 4594.2062426495. The cubic root of 21106731 is about 276.3590291907.

Adding to 21106731 its reverse (13760112), we get a palindrome (34866843).

The spelling of 21106731 in words is "twenty-one million, one hundred six thousand, seven hundred thirty-one".