21406213057 has 2 divisors, whose sum is σ = 21406213058. Its totient is φ = 21406213056.

The previous prime is 21406213019. The next prime is 21406213069. The reversal of 21406213057 is 75031260412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11457347521 + 9948865536 = 107039^2 + 99744^2 .

It is a cyclic number.

It is not a de Polignac number, because 21406213057 - 2⁷ = 21406212929 is a prime.

It is not a weakly prime, because it can be changed into another prime (21406210057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10703106528 + 10703106529.

It is an arithmetic number, because the mean of its divisors is an integer number (10703106529).

Almost surely, 2^21406213057 is an apocalyptic number.

It is an amenable number.

21406213057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21406213057 is an equidigital number, since it uses as much as digits as its factorization.

21406213057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 31.

Adding to 21406213057 its reverse (75031260412), we get a palindrome (96437473469).

The spelling of 21406213057 in words is "twenty-one billion, four hundred six million, two hundred thirteen thousand, fifty-seven".