21204232157 has 2 divisors, whose sum is σ = 21204232158. Its totient is φ = 21204232156.

The previous prime is 21204232099. The next prime is 21204232163. The reversal of 21204232157 is 75123240212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15430359961 + 5773872196 = 124219^2 + 75986^2 .

It is a cyclic number.

It is not a de Polignac number, because 21204232157 - 2¹⁰ = 21204231133 is a prime.

It is a super-2 number, since 2×21204232157² (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 (21204234157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602116078 + 10602116079.

It is an arithmetic number, because the mean of its divisors is an integer number (10602116079).

Almost surely, 2^21204232157 is an apocalyptic number.

It is an amenable number.

21204232157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21204232157 is an equidigital number, since it uses as much as digits as its factorization.

21204232157 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6720, while the sum is 29.

Adding to 21204232157 its reverse (75123240212), we get a palindrome (96327472369).

The spelling of 21204232157 in words is "twenty-one billion, two hundred four million, two hundred thirty-two thousand, one hundred fifty-seven".