21154023557 has 2 divisors, whose sum is σ = 21154023558. Its totient is φ = 21154023556.

The previous prime is 21154023511. The next prime is 21154023563. The reversal of 21154023557 is 75532045112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20059340161 + 1094683396 = 141631^2 + 33086^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154023557 - 2¹² = 21154019461 is a prime.

It is a super-2 number, since 2×21154023557² (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 (21154023577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577011778 + 10577011779.

It is an arithmetic number, because the mean of its divisors is an integer number (10577011779).

Almost surely, 2^21154023557 is an apocalyptic number.

It is an amenable number.

21154023557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154023557 is an equidigital number, since it uses as much as digits as its factorization.

21154023557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42000, while the sum is 35.

Adding to 21154023557 its reverse (75532045112), we get a palindrome (96686068669).

The spelling of 21154023557 in words is "twenty-one billion, one hundred fifty-four million, twenty-three thousand, five hundred fifty-seven".