21544844537 has 2 divisors, whose sum is σ = 21544844538. Its totient is φ = 21544844536.

The previous prime is 21544844507. The next prime is 21544844551. The reversal of 21544844537 is 73544844512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12640280041 + 8904564496 = 112429^2 + 94364^2 .

It is a cyclic number.

It is not a de Polignac number, because 21544844537 - 2¹⁸ = 21544582393 is a prime.

It is a super-2 number, since 2×21544844537² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21544844491 and 21544844500.

It is not a weakly prime, because it can be changed into another prime (21544844507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10772422268 + 10772422269.

It is an arithmetic number, because the mean of its divisors is an integer number (10772422269).

Almost surely, 2^21544844537 is an apocalyptic number.

It is an amenable number.

21544844537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21544844537 is an equidigital number, since it uses as much as digits as its factorization.

21544844537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2150400, while the sum is 47.

The spelling of 21544844537 in words is "twenty-one billion, five hundred forty-four million, eight hundred forty-four thousand, five hundred thirty-seven".