21601216157 has 2 divisors, whose sum is σ = 21601216158. Its totient is φ = 21601216156.

The previous prime is 21601216139. The next prime is 21601216163. The reversal of 21601216157 is 75161210612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20433558916 + 1167657241 = 142946^2 + 34171^2 .

It is a cyclic number.

It is not a de Polignac number, because 21601216157 - 2¹⁰ = 21601215133 is a prime.

It is a super-2 number, since 2×21601216157² (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 (21601216177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10800608078 + 10800608079.

It is an arithmetic number, because the mean of its divisors is an integer number (10800608079).

Almost surely, 2^21601216157 is an apocalyptic number.

It is an amenable number.

21601216157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21601216157 is an equidigital number, since it uses as much as digits as its factorization.

21601216157 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 32.

Adding to 21601216157 its reverse (75161210612), we get a palindrome (96762426769).

The spelling of 21601216157 in words is "twenty-one billion, six hundred one million, two hundred sixteen thousand, one hundred fifty-seven".