21394039897 has 2 divisors, whose sum is σ = 21394039898. Its totient is φ = 21394039896.

The previous prime is 21394039883. The next prime is 21394039903. The reversal of 21394039897 is 79893049312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20892100681 + 501939216 = 144541^2 + 22404^2 .

It is a cyclic number.

It is not a de Polignac number, because 21394039897 - 2²⁷ = 21259822169 is a prime.

It is a super-2 number, since 2×21394039897² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21394036897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10697019948 + 10697019949.

It is an arithmetic number, because the mean of its divisors is an integer number (10697019949).

Almost surely, 2^21394039897 is an apocalyptic number.

It is an amenable number.

21394039897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21394039897 is an equidigital number, since it uses as much as digits as its factorization.

21394039897 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2939328, while the sum is 55.

The spelling of 21394039897 in words is "twenty-one billion, three hundred ninety-four million, thirty-nine thousand, eight hundred ninety-seven".