9787661821 has 8 divisors (see below), whose sum is σ = 11843893440. Its totient is φ = 7895928768.

The previous prime is 9787661813. The next prime is 9787661833. The reversal of 9787661821 is 1281667879.

9787661821 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 9787661821 - 2³ = 9787661813 is a prime.

It is a super-2 number, since 2×9787661821² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9787661801) 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, 41124511 + ... + 41124748.

It is an arithmetic number, because the mean of its divisors is an integer number (1480486680).

Almost surely, 2^9787661821 is an apocalyptic number.

It is an amenable number.

9787661821 is a deficient number, since it is larger than the sum of its proper divisors (2056231619).

9787661821 is a wasteful number, since it uses less digits than its factorization.

9787661821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82249283.

The product of its digits is 2032128, while the sum is 55.

The square root of 9787661821 is about 98932.6125248899. The cubic root of 9787661821 is about 2139.0765093448.

The spelling of 9787661821 in words is "nine billion, seven hundred eighty-seven million, six hundred sixty-one thousand, eight hundred twenty-one".