21047297881 has 2 divisors, whose sum is σ = 21047297882. Its totient is φ = 21047297880.

The previous prime is 21047297879. The next prime is 21047297911. The reversal of 21047297881 is 18879274012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17871411856 + 3175886025 = 133684^2 + 56355^2 .

It is a cyclic number.

It is not a de Polignac number, because 21047297881 - 2¹ = 21047297879 is a prime.

It is a super-2 number, since 2×21047297881² (a number of 21 digits) contains 22 as substring.

Together with 21047297879, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21047297801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10523648940 + 10523648941.

It is an arithmetic number, because the mean of its divisors is an integer number (10523648941).

Almost surely, 2^21047297881 is an apocalyptic number.

It is an amenable number.

21047297881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21047297881 is an equidigital number, since it uses as much as digits as its factorization.

21047297881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 451584, while the sum is 49.

The spelling of 21047297881 in words is "twenty-one billion, forty-seven million, two hundred ninety-seven thousand, eight hundred eighty-one".