9921690 has 56 divisors (see below), whose sum is σ = 26795988. Its totient is φ = 2643840.

The previous prime is 9921679. The next prime is 9921731. The reversal of 9921690 is 961299.

9921690 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 9308601 + 613089 = 3051^2 + 783^2 .

It is a super-2 number, since 2×9921690² = 196879864912200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 6610 + ... + 7970.

Almost surely, 2^9921690 is an apocalyptic number.

9921690 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 9921690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (13397994).

9921690 is an abundant number, since it is smaller than the sum of its proper divisors (16874298).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9921690 is a wasteful number, since it uses less digits than its factorization.

9921690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1386 (or 1371 counting only the distinct ones).

The product of its (nonzero) digits is 8748, while the sum is 36.

The square root of 9921690 is about 3149.8714259474. The cubic root of 9921690 is about 214.8796153171.

The spelling of 9921690 in words is "nine million, nine hundred twenty-one thousand, six hundred ninety".