209139840 has 768 divisors, whose sum is σ = 976752000. Its totient is φ = 41803776.

The previous prime is 209139839. The next prime is 209139863. The reversal of 209139840 is 48931902.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 209139795 and 209139804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 11007351 + ... + 11007369.

Almost surely, 2^209139840 is an apocalyptic number.

209139840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 209139840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (488376000).

209139840 is an abundant number, since it is smaller than the sum of its proper divisors (767612160).

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

209139840 is a wasteful number, since it uses less digits than its factorization.

209139840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74 (or 49 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 209139840 is about 14461.6679535937. The cubic root of 209139840 is about 593.5795412434.

The spelling of 209139840 in words is "two hundred nine million, one hundred thirty-nine thousand, eight hundred forty".