9891457721 has 8 divisors (see below), whose sum is σ = 10255654080. Its totient is φ = 9528802192.

The previous prime is 9891457691. The next prime is 9891457753. The reversal of 9891457721 is 1277541989.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9891457721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9891457781) 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, 372125 + ... + 397818.

It is an arithmetic number, because the mean of its divisors is an integer number (1281956760).

Almost surely, 2^9891457721 is an apocalyptic number.

It is an amenable number.

9891457721 is a deficient number, since it is larger than the sum of its proper divisors (364196359).

9891457721 is a wasteful number, since it uses less digits than its factorization.

9891457721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 770415.

The product of its digits is 1270080, while the sum is 53.

The square root of 9891457721 is about 99455.8078796809. The cubic root of 9891457721 is about 2146.6114077819.

The spelling of 9891457721 in words is "nine billion, eight hundred ninety-one million, four hundred fifty-seven thousand, seven hundred twenty-one".