1917138990 has 64 divisors (see below), whose sum is σ = 4980419136. Its totient is φ = 469496832.

The previous prime is 1917138973. The next prime is 1917138997. The reversal of 1917138990 is 998317191.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1917138997) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 64354 + ... + 89306.

It is an arithmetic number, because the mean of its divisors is an integer number (77819049).

Almost surely, 2^1917138990 is an apocalyptic number.

1917138990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1917138990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2490209568).

1917138990 is an abundant number, since it is smaller than the sum of its proper divisors (3063280146).

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

1917138990 is a wasteful number, since it uses less digits than its factorization.

1917138990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25173.

The product of its (nonzero) digits is 122472, while the sum is 48.

The square root of 1917138990 is about 43785.1457688564. The cubic root of 1917138990 is about 1242.2753466500.

The spelling of 1917138990 in words is "one billion, nine hundred seventeen million, one hundred thirty-eight thousand, nine hundred ninety".