381211661 has 2 divisors, whose sum is σ = 381211662. Its totient is φ = 381211660.

The previous prime is 381211651. The next prime is 381211697. The reversal of 381211661 is 166112183.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 350064100 + 31147561 = 18710^2 + 5581^2 .

It is a cyclic number.

It is not a de Polignac number, because 381211661 - 2²⁶ = 314102797 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (381211601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 190605830 + 190605831.

It is an arithmetic number, because the mean of its divisors is an integer number (190605831).

Almost surely, 2^381211661 is an apocalyptic number.

It is an amenable number.

381211661 is a deficient number, since it is larger than the sum of its proper divisors (1).

381211661 is an equidigital number, since it uses as much as digits as its factorization.

381211661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 381211661 is about 19524.6424038956. The cubic root of 381211661 is about 725.0846740581.

The spelling of 381211661 in words is "three hundred eighty-one million, two hundred eleven thousand, six hundred sixty-one".