21205233997 has 2 divisors, whose sum is σ = 21205233998. Its totient is φ = 21205233996.

The previous prime is 21205233967. The next prime is 21205234051. The reversal of 21205233997 is 79933250212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20833746921 + 371487076 = 144339^2 + 19274^2 .

It is a cyclic number.

It is not a de Polignac number, because 21205233997 - 2¹⁹ = 21204709709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21205233967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602616998 + 10602616999.

It is an arithmetic number, because the mean of its divisors is an integer number (10602616999).

Almost surely, 2^21205233997 is an apocalyptic number.

It is an amenable number.

21205233997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21205233997 is an equidigital number, since it uses as much as digits as its factorization.

21205233997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 204120, while the sum is 43.

The spelling of 21205233997 in words is "twenty-one billion, two hundred five million, two hundred thirty-three thousand, nine hundred ninety-seven".