21623131 has 2 divisors, whose sum is σ = 21623132. Its totient is φ = 21623130.

The previous prime is 21623101. The next prime is 21623137. The reversal of 21623131 is 13132612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21623131 is a prime.

It is a super-2 number, since 2×21623131² = 935119588486322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21623099 and 21623108.

It is not a weakly prime, because it can be changed into another prime (21623137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10811565 + 10811566.

It is an arithmetic number, because the mean of its divisors is an integer number (10811566).

Almost surely, 2^21623131 is an apocalyptic number.

21623131 is a deficient number, since it is larger than the sum of its proper divisors (1).

21623131 is an equidigital number, since it uses as much as digits as its factorization.

21623131 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216, while the sum is 19.

The square root of 21623131 is about 4650.0678489674. The cubic root of 21623131 is about 278.5947062105.

Adding to 21623131 its reverse (13132612), we get a palindrome (34755743).

The spelling of 21623131 in words is "twenty-one million, six hundred twenty-three thousand, one hundred thirty-one".