21181739 has 2 divisors, whose sum is σ = 21181740. Its totient is φ = 21181738.

The previous prime is 21181729. The next prime is 21181777. The reversal of 21181739 is 93718112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21181739 - 2⁸ = 21181483 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21181729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10590869 + 10590870.

It is an arithmetic number, because the mean of its divisors is an integer number (10590870).

Almost surely, 2^21181739 is an apocalyptic number.

21181739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21181739 is an equidigital number, since it uses as much as digits as its factorization.

21181739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 32.

The square root of 21181739 is about 4602.3623281962. The cubic root of 21181739 is about 276.6860122599.

The spelling of 21181739 in words is "twenty-one million, one hundred eighty-one thousand, seven hundred thirty-nine".