21980435857 has 2 divisors, whose sum is σ = 21980435858. Its totient is φ = 21980435856.

The previous prime is 21980435843. The next prime is 21980435879. The reversal of 21980435857 is 75853408912.

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., 16704011536 + 5276424321 = 129244^2 + 72639^2 .

It is a cyclic number.

It is not a de Polignac number, because 21980435857 - 2¹⁵ = 21980403089 is a prime.

It is not a weakly prime, because it can be changed into another prime (21980435887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990217928 + 10990217929.

It is an arithmetic number, because the mean of its divisors is an integer number (10990217929).

Almost surely, 2^21980435857 is an apocalyptic number.

It is an amenable number.

21980435857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21980435857 is an equidigital number, since it uses as much as digits as its factorization.

21980435857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2419200, while the sum is 52.

The spelling of 21980435857 in words is "twenty-one billion, nine hundred eighty million, four hundred thirty-five thousand, eight hundred fifty-seven".