21437723 has 2 divisors, whose sum is σ = 21437724. Its totient is φ = 21437722.

The previous prime is 21437701. The next prime is 21437747. The reversal of 21437723 is 32773412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21437723 - 2¹⁶ = 21372187 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21437753) 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, 10718861 + 10718862.

It is an arithmetic number, because the mean of its divisors is an integer number (10718862).

Almost surely, 2^21437723 is an apocalyptic number.

21437723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21437723 is an equidigital number, since it uses as much as digits as its factorization.

21437723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7056, while the sum is 29.

The square root of 21437723 is about 4630.0888760368. The cubic root of 21437723 is about 277.7961473304.

The spelling of 21437723 in words is "twenty-one million, four hundred thirty-seven thousand, seven hundred twenty-three".