1621001491 has 2 divisors, whose sum is σ = 1621001492. Its totient is φ = 1621001490.

The previous prime is 1621001479. The next prime is 1621001509. The reversal of 1621001491 is 1941001261.

It is a weak prime.

It is an emirp because it is prime and its reverse (1941001261) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1621001491 - 2¹⁹ = 1620477203 is a prime.

It is not a weakly prime, because it can be changed into another prime (1621001441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810500745 + 810500746.

It is an arithmetic number, because the mean of its divisors is an integer number (810500746).

Almost surely, 2^1621001491 is an apocalyptic number.

1621001491 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621001491 is an equidigital number, since it uses as much as digits as its factorization.

1621001491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 1621001491 is about 40261.6627947729. The cubic root of 1621001491 is about 1174.7022613046.

The spelling of 1621001491 in words is "one billion, six hundred twenty-one million, one thousand, four hundred ninety-one".