21211958857 has 2 divisors, whose sum is σ = 21211958858. Its totient is φ = 21211958856.

The previous prime is 21211958849. The next prime is 21211958897. The reversal of 21211958857 is 75885911212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13330780681 + 7881178176 = 115459^2 + 88776^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211958857 - 2³ = 21211958849 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21211958857.

It is not a weakly prime, because it can be changed into another prime (21211958837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605979428 + 10605979429.

It is an arithmetic number, because the mean of its divisors is an integer number (10605979429).

Almost surely, 2^21211958857 is an apocalyptic number.

It is an amenable number.

21211958857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211958857 is an equidigital number, since it uses as much as digits as its factorization.

21211958857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 49.

The spelling of 21211958857 in words is "twenty-one billion, two hundred eleven million, nine hundred fifty-eight thousand, eight hundred fifty-seven".