21679970549 has 2 divisors, whose sum is σ = 21679970550. Its totient is φ = 21679970548.

The previous prime is 21679970531. The next prime is 21679970573. The reversal of 21679970549 is 94507997612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13733496100 + 7946474449 = 117190^2 + 89143^2 .

It is a cyclic number.

It is not a de Polignac number, because 21679970549 - 2⁸ = 21679970293 is a prime.

It is a super-2 number, since 2×21679970549² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21679970519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10839985274 + 10839985275.

It is an arithmetic number, because the mean of its divisors is an integer number (10839985275).

Almost surely, 2^21679970549 is an apocalyptic number.

It is an amenable number.

21679970549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21679970549 is an equidigital number, since it uses as much as digits as its factorization.

21679970549 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8573040, while the sum is 59.

The spelling of 21679970549 in words is "twenty-one billion, six hundred seventy-nine million, nine hundred seventy thousand, five hundred forty-nine".