19739721 has 4 divisors (see below), whose sum is σ = 26319632. Its totient is φ = 13159812.

The previous prime is 19739719. The next prime is 19739723. The reversal of 19739721 is 12793791.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12793791 = 3 ⋅4264597.

It is an interprime number because it is at equal distance from previous prime (19739719) and next prime (19739723).

It is not a de Polignac number, because 19739721 - 2¹ = 19739719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19739721.

It is not an unprimeable number, because it can be changed into a prime (19739723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3289951 + ... + 3289956.

It is an arithmetic number, because the mean of its divisors is an integer number (6579908).

Almost surely, 2^19739721 is an apocalyptic number.

It is an amenable number.

19739721 is a deficient number, since it is larger than the sum of its proper divisors (6579911).

19739721 is an equidigital number, since it uses as much as digits as its factorization.

19739721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6579910.

The product of its digits is 23814, while the sum is 39.

The square root of 19739721 is about 4442.9405802914. The cubic root of 19739721 is about 270.2591065491.

The spelling of 19739721 in words is "nineteen million, seven hundred thirty-nine thousand, seven hundred twenty-one".