21719597 has 2 divisors, whose sum is σ = 21719598. Its totient is φ = 21719596.

The previous prime is 21719573. The next prime is 21719647. The reversal of 21719597 is 79591712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11600836 + 10118761 = 3406^2 + 3181^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21719597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21719197) 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, 10859798 + 10859799.

It is an arithmetic number, because the mean of its divisors is an integer number (10859799).

Almost surely, 2^21719597 is an apocalyptic number.

It is an amenable number.

21719597 is a deficient number, since it is larger than the sum of its proper divisors (1).

21719597 is an equidigital number, since it uses as much as digits as its factorization.

21719597 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39690, while the sum is 41.

The square root of 21719597 is about 4660.4288429285. The cubic root of 21719597 is about 279.0083843611.

The spelling of 21719597 in words is "twenty-one million, seven hundred nineteen thousand, five hundred ninety-seven".