21478304557 has 2 divisors, whose sum is σ = 21478304558. Its totient is φ = 21478304556.

The previous prime is 21478304489. The next prime is 21478304591. The reversal of 21478304557 is 75540387412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21401934436 + 76370121 = 146294^2 + 8739^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21478304557 is a prime.

It is a super-2 number, since 2×21478304557² (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 (21478305557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739152278 + 10739152279.

It is an arithmetic number, because the mean of its divisors is an integer number (10739152279).

Almost surely, 2^21478304557 is an apocalyptic number.

It is an amenable number.

21478304557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478304557 is an equidigital number, since it uses as much as digits as its factorization.

21478304557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 940800, while the sum is 46.

The spelling of 21478304557 in words is "twenty-one billion, four hundred seventy-eight million, three hundred four thousand, five hundred fifty-seven".