1621663451 has 2 divisors, whose sum is σ = 1621663452. Its totient is φ = 1621663450.

The previous prime is 1621663427. The next prime is 1621663583. The reversal of 1621663451 is 1543661261.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1621663451 - 2⁶ = 1621663387 is a prime.

It is not a weakly prime, because it can be changed into another prime (1621663651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810831725 + 810831726.

It is an arithmetic number, because the mean of its divisors is an integer number (810831726).

Almost surely, 2^1621663451 is an apocalyptic number.

1621663451 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621663451 is an equidigital number, since it uses as much as digits as its factorization.

1621663451 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 35.

The square root of 1621663451 is about 40269.8826792431. The cubic root of 1621663451 is about 1174.8621419069.

The spelling of 1621663451 in words is "one billion, six hundred twenty-one million, six hundred sixty-three thousand, four hundred fifty-one".