21034533991 has 2 divisors, whose sum is σ = 21034533992. Its totient is φ = 21034533990.

The previous prime is 21034533967. The next prime is 21034534021. The reversal of 21034533991 is 19933543012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21034533991 - 2⁹ = 21034533479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21034533391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10517266995 + 10517266996.

It is an arithmetic number, because the mean of its divisors is an integer number (10517266996).

Almost surely, 2^21034533991 is an apocalyptic number.

21034533991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21034533991 is an equidigital number, since it uses as much as digits as its factorization.

21034533991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 87480, while the sum is 40.

It can be divided in two parts, 21034 and 533991, that added together give a square (555025 = 745²).

The spelling of 21034533991 in words is "twenty-one billion, thirty-four million, five hundred thirty-three thousand, nine hundred ninety-one".