21020012399 has 2 divisors, whose sum is σ = 21020012400. Its totient is φ = 21020012398.

The previous prime is 21020012393. The next prime is 21020012413. The reversal of 21020012399 is 99321002012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020012399 is a prime.

It is a super-2 number, since 2×21020012399² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020012393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510006199 + 10510006200.

It is an arithmetic number, because the mean of its divisors is an integer number (10510006200).

Almost surely, 2^21020012399 is an apocalyptic number.

21020012399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020012399 is an equidigital number, since it uses as much as digits as its factorization.

21020012399 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 29.

The spelling of 21020012399 in words is "twenty-one billion, twenty million, twelve thousand, three hundred ninety-nine".