19989551621 has 8 divisors (see below), whose sum is σ = 21799706880. Its totient is φ = 18218324592.

The previous prime is 19989551591. The next prime is 19989551629. The reversal of 19989551621 is 12615598991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-19989551621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19989551629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9730985 + ... + 9733038.

It is an arithmetic number, because the mean of its divisors is an integer number (2724963360).

Almost surely, 2^19989551621 is an apocalyptic number.

It is an amenable number.

19989551621 is a deficient number, since it is larger than the sum of its proper divisors (1810155259).

19989551621 is a wasteful number, since it uses less digits than its factorization.

19989551621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19464115.

The product of its digits is 1749600, while the sum is 56.

The spelling of 19989551621 in words is "nineteen billion, nine hundred eighty-nine million, five hundred fifty-one thousand, six hundred twenty-one".