1721651 has 2 divisors, whose sum is σ = 1721652. Its totient is φ = 1721650.

The previous prime is 1721639. The next prime is 1721659. The reversal of 1721651 is 1561271.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1721651 - 2¹⁴ = 1705267 is a prime.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1721659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860825 + 860826.

It is an arithmetic number, because the mean of its divisors is an integer number (860826).

2^1721651 is an apocalyptic number.

1721651 is a deficient number, since it is larger than the sum of its proper divisors (1).

1721651 is an equidigital number, since it uses as much as digits as its factorization.

1721651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 420, while the sum is 23.

The square root of 1721651 is about 1312.1169917351. The cubic root of 1721651 is about 119.8528520435.

The spelling of 1721651 in words is "one million, seven hundred twenty-one thousand, six hundred fifty-one".