1621208865631 has 4 divisors (see below), whose sum is σ = 1622030564952. Its totient is φ = 1620387166312.

The previous prime is 1621208865607. The next prime is 1621208865649. The reversal of 1621208865631 is 1365688021261.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1621208865631 - 2¹³ = 1621208857439 is a prime.

It is a super-2 number, since 2×1621208865631² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721208865631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 410846701 + ... + 410850646.

It is an arithmetic number, because the mean of its divisors is an integer number (405507641238).

Almost surely, 2^{1621208865631} is an apocalyptic number.

1621208865631 is a deficient number, since it is larger than the sum of its proper divisors (821699321).

1621208865631 is an equidigital number, since it uses as much as digits as its factorization.

1621208865631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 821699320.

The product of its (nonzero) digits is 829440, while the sum is 49.

The spelling of 1621208865631 in words is "one trillion, six hundred twenty-one billion, two hundred eight million, eight hundred sixty-five thousand, six hundred thirty-one".