21031894993 has 2 divisors, whose sum is σ = 21031894994. Its totient is φ = 21031894992.

The previous prime is 21031894987. The next prime is 21031894999. The reversal of 21031894993 is 39949813012.

It is a balanced prime because it is at equal distance from previous prime (21031894987) and next prime (21031894999).

It can be written as a sum of positive squares in only one way, i.e., 20650552209 + 381342784 = 143703^2 + 19528^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21031894993 is a prime.

It is not a weakly prime, because it can be changed into another prime (21031894999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515947496 + 10515947497.

It is an arithmetic number, because the mean of its divisors is an integer number (10515947497).

Almost surely, 2^21031894993 is an apocalyptic number.

It is an amenable number.

21031894993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21031894993 is an equidigital number, since it uses as much as digits as its factorization.

21031894993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 419904, while the sum is 49.

The spelling of 21031894993 in words is "twenty-one billion, thirty-one million, eight hundred ninety-four thousand, nine hundred ninety-three".