21719749 has 2 divisors, whose sum is σ = 21719750. Its totient is φ = 21719748.

The previous prime is 21719743. The next prime is 21719759. The reversal of 21719749 is 94791712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21095649 + 624100 = 4593^2 + 790^2 .

It is a cyclic number.

It is not a de Polignac number, because 21719749 - 2³ = 21719741 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21719741) 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, 10859874 + 10859875.

It is an arithmetic number, because the mean of its divisors is an integer number (10859875).

Almost surely, 2^21719749 is an apocalyptic number.

It is an amenable number.

21719749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21719749 is an equidigital number, since it uses as much as digits as its factorization.

21719749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31752, while the sum is 40.

The square root of 21719749 is about 4660.4451504121. The cubic root of 21719749 is about 279.0090352200.

The spelling of 21719749 in words is "twenty-one million, seven hundred nineteen thousand, seven hundred forty-nine".