209978398756 has 81 divisors (see below), whose sum is σ = 434503849521. Its totient is φ = 88530808800.

The previous prime is 209978398741. The next prime is 209978398757. The reversal of 209978398756 is 657893879902.

The square root of 209978398756 is 458234.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 67306000356 + 142672398400 = 259434^2 + 377720^2 .

It is not an unprimeable number, because it can be changed into a prime (209978398757) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 455484366 + ... + 455484826.

Almost surely, 2^209978398756 is an apocalyptic number.

209978398756 is the 458234-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 209978398756

209978398756 is an abundant number, since it is smaller than the sum of its proper divisors (224525450765).

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

209978398756 is an frugal number, since it uses more digits than its factorization.

209978398756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1082 (or 541 counting only the distinct ones).

The product of its (nonzero) digits is 411505920, while the sum is 73.

The spelling of 209978398756 in words is "two hundred nine billion, nine hundred seventy-eight million, three hundred ninety-eight thousand, seven hundred fifty-six".