1621681693 has 2 divisors, whose sum is σ = 1621681694. Its totient is φ = 1621681692.

The previous prime is 1621681687. The next prime is 1621681717. The reversal of 1621681693 is 3961861261.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1027394809 + 594286884 = 32053^2 + 24378^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621681693 - 2²¹ = 1619584541 is a prime.

It is a super-2 number, since 2×1621681693² = 5259703026822692498, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621681643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810840846 + 810840847.

It is an arithmetic number, because the mean of its divisors is an integer number (810840847).

Almost surely, 2^1621681693 is an apocalyptic number.

It is an amenable number.

1621681693 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621681693 is an equidigital number, since it uses as much as digits as its factorization.

1621681693 is an evil number, because the sum of its binary digits is even.

The product of its digits is 93312, while the sum is 43.

The square root of 1621681693 is about 40270.1091754169. The cubic root of 1621681693 is about 1174.8665472095.

The spelling of 1621681693 in words is "one billion, six hundred twenty-one million, six hundred eighty-one thousand, six hundred ninety-three".