72131531621 has 2 divisors, whose sum is σ = 72131531622. Its totient is φ = 72131531620.

The previous prime is 72131531533. The next prime is 72131531701. The reversal of 72131531621 is 12613513127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48358209025 + 23773322596 = 219905^2 + 154186^2 .

It is a cyclic number.

It is not a de Polignac number, because 72131531621 - 2¹⁴ = 72131515237 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72131536621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36065765810 + 36065765811.

It is an arithmetic number, because the mean of its divisors is an integer number (36065765811).

Almost surely, 2^72131531621 is an apocalyptic number.

It is an amenable number.

72131531621 is a deficient number, since it is larger than the sum of its proper divisors (1).

72131531621 is an equidigital number, since it uses as much as digits as its factorization.

72131531621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7560, while the sum is 32.

The spelling of 72131531621 in words is "seventy-two billion, one hundred thirty-one million, five hundred thirty-one thousand, six hundred twenty-one".