1662721 has 4 divisors (see below), whose sum is σ = 1685572. Its totient is φ = 1639872.

The previous prime is 1662707. The next prime is 1662733. The reversal of 1662721 is 1272661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1254400 + 408321 = 1120^2 + 639^2 .

It is not a de Polignac number, because 1662721 - 2⁷ = 1662593 is a prime.

It is a super-2 number, since 2×1662721² = 5529282247682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1662701) 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, 11316 + ... + 11461.

It is an arithmetic number, because the mean of its divisors is an integer number (421393).

2^1662721 is an apocalyptic number.

It is an amenable number.

1662721 is a deficient number, since it is larger than the sum of its proper divisors (22851).

1662721 is an equidigital number, since it uses as much as digits as its factorization.

1662721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22850.

The product of its digits is 1008, while the sum is 25.

The square root of 1662721 is about 1289.4653930990. The cubic root of 1662721 is about 118.4694741171.

The spelling of 1662721 in words is "one million, six hundred sixty-two thousand, seven hundred twenty-one".