21731123 has 2 divisors, whose sum is σ = 21731124. Its totient is φ = 21731122.

The previous prime is 21731119. The next prime is 21731131. The reversal of 21731123 is 32113712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21731123 - 2² = 21731119 is a prime.

It is a super-2 number, since 2×21731123² = 944483413682258, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 21731095 and 21731104.

It is not a weakly prime, because it can be changed into another prime (21731623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865561 + 10865562.

It is an arithmetic number, because the mean of its divisors is an integer number (10865562).

Almost surely, 2^21731123 is an apocalyptic number.

21731123 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731123 is an equidigital number, since it uses as much as digits as its factorization.

21731123 is an evil number, because the sum of its binary digits is even.

The product of its digits is 252, while the sum is 20.

The square root of 21731123 is about 4661.6652603978. The cubic root of 21731123 is about 279.0577296897.

Adding to 21731123 its reverse (32113712), we get a palindrome (53844835).

The spelling of 21731123 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred twenty-three".