1620391 has 2 divisors, whose sum is σ = 1620392. Its totient is φ = 1620390.

The previous prime is 1620379. The next prime is 1620403. The reversal of 1620391 is 1930261.

It is a balanced prime because it is at equal distance from previous prime (1620379) and next prime (1620403).

It is an emirp because it is prime and its reverse (1930261) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1620391 is a prime.

It is equal to p₁₂₂₅₆₆ and since 1620391 and 122566 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1620331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810195 + 810196.

It is an arithmetic number, because the mean of its divisors is an integer number (810196).

2^1620391 is an apocalyptic number.

1620391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1620391 is an equidigital number, since it uses as much as digits as its factorization.

1620391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 22.

The square root of 1620391 is about 1272.9457961752. The cubic root of 1620391 is about 117.4554773222.

The spelling of 1620391 in words is "one million, six hundred twenty thousand, three hundred ninety-one".