21352051997 has 2 divisors, whose sum is σ = 21352051998. Its totient is φ = 21352051996.

The previous prime is 21352051961. The next prime is 21352052023. The reversal of 21352051997 is 79915025312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14911828996 + 6440223001 = 122114^2 + 80251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21352051997 - 2⁸ = 21352051741 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21352051927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10676025998 + 10676025999.

It is an arithmetic number, because the mean of its divisors is an integer number (10676025999).

Almost surely, 2^21352051997 is an apocalyptic number.

It is an amenable number.

21352051997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21352051997 is an equidigital number, since it uses as much as digits as its factorization.

21352051997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 170100, while the sum is 44.

The spelling of 21352051997 in words is "twenty-one billion, three hundred fifty-two million, fifty-one thousand, nine hundred ninety-seven".