21400031 has 2 divisors, whose sum is σ = 21400032. Its totient is φ = 21400030.

The previous prime is 21400003. The next prime is 21400037. The reversal of 21400031 is 13000412.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21400031 - 2⁶ = 21399967 is a prime.

It is a super-2 number, since 2×21400031² = 915922653601922, which contains 22 as substring.

It is a Chen prime.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21399985 and 21400021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21400037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700015 + 10700016.

It is an arithmetic number, because the mean of its divisors is an integer number (10700016).

Almost surely, 2^21400031 is an apocalyptic number.

21400031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21400031 is an equidigital number, since it uses as much as digits as its factorization.

21400031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21400031 is about 4626.0167531041. The cubic root of 21400031 is about 277.6332439141.

Adding to 21400031 its reverse (13000412), we get a palindrome (34400443).

The spelling of 21400031 in words is "twenty-one million, four hundred thousand, thirty-one".