9921621870 has 48 divisors (see below), whose sum is σ = 25828770240. Its totient is φ = 2642427072.

The previous prime is 9921621869. The next prime is 9921621883. The reversal of 9921621870 is 781261299.

It is a Harshad number since it is a multiple of its sum of digits (45).

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 23 ways as a sum of consecutive naturals, for example, 2571 + ... + 140889.

It is an arithmetic number, because the mean of its divisors is an integer number (538099380).

Almost surely, 2^9921621870 is an apocalyptic number.

9921621870 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

9921621870 is an abundant number, since it is smaller than the sum of its proper divisors (15907148370).

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

9921621870 is a wasteful number, since it uses less digits than its factorization.

9921621870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139129 (or 139126 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 9921621870 is about 99607.3384344748. The cubic root of 9921621870 is about 2148.7912347275.

The spelling of 9921621870 in words is "nine billion, nine hundred twenty-one million, six hundred twenty-one thousand, eight hundred seventy".