21121534537 has 2 divisors, whose sum is σ = 21121534538. Its totient is φ = 21121534536.

The previous prime is 21121534523. The next prime is 21121534543. The reversal of 21121534537 is 73543512112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11633995321 + 9487539216 = 107861^2 + 97404^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121534537 is a prime.

It is a super-2 number, since 2×21121534537² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21121534517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560767268 + 10560767269.

It is an arithmetic number, because the mean of its divisors is an integer number (10560767269).

Almost surely, 2^21121534537 is an apocalyptic number.

It is an amenable number.

21121534537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121534537 is an equidigital number, since it uses as much as digits as its factorization.

21121534537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25200, while the sum is 34.

The spelling of 21121534537 in words is "twenty-one billion, one hundred twenty-one million, five hundred thirty-four thousand, five hundred thirty-seven".