1661751 has 24 divisors (see below), whose sum is σ = 2955680. Its totient is φ = 876096.

The previous prime is 1661741. The next prime is 1661789. The reversal of 1661751 is 1571661.

1661751 = 338² + 339² + ... + 351².

It is not a de Polignac number, because 1661751 - 2⁷ = 1661623 is a prime.

It is a super-2 number, since 2×1661751² = 5522832772002, which contains 22 as substring.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 196 + ... + 1833.

2^1661751 is an apocalyptic number.

1661751 is a deficient number, since it is larger than the sum of its proper divisors (1293929).

1661751 is a wasteful number, since it uses less digits than its factorization.

1661751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2055 (or 2052 counting only the distinct ones).

The product of its digits is 1260, while the sum is 27.

The square root of 1661751 is about 1289.0892133596. The cubic root of 1661751 is about 118.4464320185.

It can be divided in two parts, 166175 and 1, that added together give a triangular number (166176 = T₅₇₆).

The spelling of 1661751 in words is "one million, six hundred sixty-one thousand, seven hundred fifty-one".