19720657 has 4 divisors (see below), whose sum is σ = 21513456. Its totient is φ = 17927860.

The previous prime is 19720639. The next prime is 19720661. The reversal of 19720657 is 75602791.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19720657 - 2¹¹ = 19718609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19720457) 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 in 3 ways as a sum of consecutive naturals, for example, 896383 + ... + 896404.

It is an arithmetic number, because the mean of its divisors is an integer number (5378364).

Almost surely, 2^19720657 is an apocalyptic number.

It is an amenable number.

19720657 is a deficient number, since it is larger than the sum of its proper divisors (1792799).

19720657 is a wasteful number, since it uses less digits than its factorization.

19720657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1792798.

The product of its (nonzero) digits is 26460, while the sum is 37.

The square root of 19720657 is about 4440.7946360984. The cubic root of 19720657 is about 270.1720759520.

The spelling of 19720657 in words is "nineteen million, seven hundred twenty thousand, six hundred fifty-seven".