1621815809231 has 4 divisors (see below), whose sum is σ = 1621818834552. Its totient is φ = 1621812783912.

The previous prime is 1621815809197. The next prime is 1621815809249. The reversal of 1621815809231 is 1329085181261.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1621815809231 is a prime.

It is a super-2 number, since 2×1621815809231² (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 (1621815859231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 468101 + ... + 1860846.

It is an arithmetic number, because the mean of its divisors is an integer number (405454708638).

Almost surely, 2^{1621815809231} is an apocalyptic number.

1621815809231 is a deficient number, since it is larger than the sum of its proper divisors (3025321).

1621815809231 is an equidigital number, since it uses as much as digits as its factorization.

1621815809231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3025320.

The product of its (nonzero) digits is 207360, while the sum is 47.

The spelling of 1621815809231 in words is "one trillion, six hundred twenty-one billion, eight hundred fifteen million, eight hundred nine thousand, two hundred thirty-one".