665632381 has 2 divisors, whose sum is σ = 665632382. Its totient is φ = 665632380.

The previous prime is 665632349. The next prime is 665632391. The reversal of 665632381 is 183236566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 559748281 + 105884100 = 23659^2 + 10290^2 .

It is a cyclic number.

It is not a de Polignac number, because 665632381 - 2⁵ = 665632349 is a prime.

It is a super-2 number, since 2×665632381² = 886132933271458322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665632321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332816190 + 332816191.

It is an arithmetic number, because the mean of its divisors is an integer number (332816191).

Almost surely, 2^665632381 is an apocalyptic number.

It is an amenable number.

665632381 is a deficient number, since it is larger than the sum of its proper divisors (1).

665632381 is an equidigital number, since it uses as much as digits as its factorization.

665632381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 155520, while the sum is 40.

The square root of 665632381 is about 25799.8523445387. The cubic root of 665632381 is about 873.1284650306.

Subtracting from 665632381 its sum of digits (40), we obtain a triangular number (665632341 = T₃₆₄₈₆).

The spelling of 665632381 in words is "six hundred sixty-five million, six hundred thirty-two thousand, three hundred eighty-one".