19720639 has 2 divisors, whose sum is σ = 19720640. Its totient is φ = 19720638.

The previous prime is 19720621. The next prime is 19720661. The reversal of 19720639 is 93602791.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19720639 - 2⁷ = 19720511 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 19720598 and 19720607.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19720669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9860319 + 9860320.

It is an arithmetic number, because the mean of its divisors is an integer number (9860320).

Almost surely, 2^19720639 is an apocalyptic number.

19720639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19720639 is an equidigital number, since it uses as much as digits as its factorization.

19720639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20412, while the sum is 37.

The square root of 19720639 is about 4440.7926094336. The cubic root of 19720639 is about 270.1719937522.

The spelling of 19720639 in words is "nineteen million, seven hundred twenty thousand, six hundred thirty-nine".