1621643 has 2 divisors, whose sum is σ = 1621644. Its totient is φ = 1621642.

The previous prime is 1621639. The next prime is 1621657. The reversal of 1621643 is 3461261.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1621643 - 2² = 1621639 is a prime.

It is a Chen prime.

It is equal to p₁₂₂₆₅₇ and since 1621643 and 122657 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (1621043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810821 + 810822.

It is an arithmetic number, because the mean of its divisors is an integer number (810822).

2^1621643 is an apocalyptic number.

1621643 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621643 is an equidigital number, since it uses as much as digits as its factorization.

1621643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 23.

The square root of 1621643 is about 1273.4374739264. The cubic root of 1621643 is about 117.4857203108.

The spelling of 1621643 in words is "one million, six hundred twenty-one thousand, six hundred forty-three".