189978521 has 2 divisors, whose sum is σ = 189978522. Its totient is φ = 189978520.

The previous prime is 189978517. The next prime is 189978527. The reversal of 189978521 is 125879981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 111408025 + 78570496 = 10555^2 + 8864^2 .

It is a cyclic number.

It is not a de Polignac number, because 189978521 - 2² = 189978517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 189978521.

It is not a weakly prime, because it can be changed into another prime (189978527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 94989260 + 94989261.

It is an arithmetic number, because the mean of its divisors is an integer number (94989261).

Almost surely, 2^189978521 is an apocalyptic number.

It is an amenable number.

189978521 is a deficient number, since it is larger than the sum of its proper divisors (1).

189978521 is an equidigital number, since it uses as much as digits as its factorization.

189978521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362880, while the sum is 50.

The square root of 189978521 is about 13783.2696048507. The cubic root of 189978521 is about 574.8680438219.

The spelling of 189978521 in words is "one hundred eighty-nine million, nine hundred seventy-eight thousand, five hundred twenty-one".