21122731 has 8 divisors (see below), whose sum is σ = 24247520. Its totient is φ = 18024768.

The previous prime is 21122719. The next prime is 21122743. The reversal of 21122731 is 13722112.

It is an interprime number because it is at equal distance from previous prime (21122719) and next prime (21122743).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21122731 - 2⁷ = 21122603 is a prime.

It is a super-2 number, since 2×21122731² = 892339529796722, 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 = 21122699 and 21122708.

It is not an unprimeable number, because it can be changed into a prime (21120731) 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, 4986 + ... + 8191.

It is an arithmetic number, because the mean of its divisors is an integer number (3030940).

Almost surely, 2^21122731 is an apocalyptic number.

21122731 is a deficient number, since it is larger than the sum of its proper divisors (3124789).

21122731 is a wasteful number, since it uses less digits than its factorization.

21122731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13413.

The product of its digits is 168, while the sum is 19.

The square root of 21122731 is about 4595.9472364247. The cubic root of 21122731 is about 276.4288430593.

Adding to 21122731 its reverse (13722112), we get a palindrome (34844843).

The spelling of 21122731 in words is "twenty-one million, one hundred twenty-two thousand, seven hundred thirty-one".