21451831 has 2 divisors, whose sum is σ = 21451832. Its totient is φ = 21451830.

The previous prime is 21451819. The next prime is 21451849. The reversal of 21451831 is 13815412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21451831 - 2⁹ = 21451319 is a prime.

It is a super-2 number, since 2×21451831² = 920362106505122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21451796 and 21451805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21451811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725915 + 10725916.

It is an arithmetic number, because the mean of its divisors is an integer number (10725916).

Almost surely, 2^21451831 is an apocalyptic number.

21451831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451831 is an equidigital number, since it uses as much as digits as its factorization.

21451831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 960, while the sum is 25.

The square root of 21451831 is about 4631.6121383380. The cubic root of 21451831 is about 277.8570724675.

The spelling of 21451831 in words is "twenty-one million, four hundred fifty-one thousand, eight hundred thirty-one".