1667521 has 4 divisors (see below), whose sum is σ = 1721344. Its totient is φ = 1613700.

The previous prime is 1667509. The next prime is 1667537. The reversal of 1667521 is 1257661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1257661 = 839 ⋅1499.

It is a cyclic number.

It is not a de Polignac number, because 1667521 - 2⁵ = 1667489 is a prime.

It is a Duffinian number.

1667521 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1667521.

It is not an unprimeable number, because it can be changed into a prime (1667551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26865 + ... + 26926.

It is an arithmetic number, because the mean of its divisors is an integer number (430336).

2^1667521 is an apocalyptic number.

It is an amenable number.

1667521 is a deficient number, since it is larger than the sum of its proper divisors (53823).

1667521 is an equidigital number, since it uses as much as digits as its factorization.

1667521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53822.

The product of its digits is 2520, while the sum is 28.

The square root of 1667521 is about 1291.3252882214. The cubic root of 1667521 is about 118.5833651726.

It can be divided in two parts, 166752 and 1, that added together give a triangular number (166753 = T₅₇₇).

The spelling of 1667521 in words is "one million, six hundred sixty-seven thousand, five hundred twenty-one".