201978 has 36 divisors (see below), whose sum is σ = 511290. Its totient is φ = 57456.

The previous prime is 201973. The next prime is 201979. The reversal of 201978 is 879102.

It can be written as a sum of positive squares in only one way, i.e., 127449 + 74529 = 357^2 + 273^2 .

It is a super-2 number, since 2×201978² = 81590224968, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (201973) by changing a digit.

201978 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 768 + ... + 996.

2²⁰¹⁹⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 201978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (255645).

201978 is an abundant number, since it is smaller than the sum of its proper divisors (309312).

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

201978 is a wasteful number, since it uses less digits than its factorization.

201978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251 (or 241 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 201978 is about 449.4196257397. The cubic root of 201978 is about 58.6725129045.

The spelling of 201978 in words is "two hundred one thousand, nine hundred seventy-eight".