21390232537 has 2 divisors, whose sum is σ = 21390232538. Its totient is φ = 21390232536.

The previous prime is 21390232477. The next prime is 21390232561. The reversal of 21390232537 is 73523209312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18556160841 + 2834071696 = 136221^2 + 53236^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21390232537 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21390232496 and 21390232505.

It is not a weakly prime, because it can be changed into another prime (21390212537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695116268 + 10695116269.

It is an arithmetic number, because the mean of its divisors is an integer number (10695116269).

Almost surely, 2^21390232537 is an apocalyptic number.

It is an amenable number.

21390232537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390232537 is an equidigital number, since it uses as much as digits as its factorization.

21390232537 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 68040, while the sum is 37.

The spelling of 21390232537 in words is "twenty-one billion, three hundred ninety million, two hundred thirty-two thousand, five hundred thirty-seven".