1661831 has 2 divisors, whose sum is σ = 1661832. Its totient is φ = 1661830.

The previous prime is 1661827. The next prime is 1661833. The reversal of 1661831 is 1381661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1661831 - 2² = 1661827 is a prime.

It is a super-2 number, since 2×1661831² = 5523364545122, which contains 22 as substring.

Together with 1661833, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1661831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661833) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830915 + 830916.

It is an arithmetic number, because the mean of its divisors is an integer number (830916).

2^1661831 is an apocalyptic number.

1661831 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661831 is an equidigital number, since it uses as much as digits as its factorization.

1661831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 26.

The square root of 1661831 is about 1289.1202426461. The cubic root of 1661831 is about 118.4483327370.

It can be divided in two parts, 1661 and 831, that multiplied together give a triangular number (1380291 = T₁₆₆₁).

The spelling of 1661831 in words is "one million, six hundred sixty-one thousand, eight hundred thirty-one".