21397991453 has 2 divisors, whose sum is σ = 21397991454. Its totient is φ = 21397991452.

The previous prime is 21397991449. The next prime is 21397991491. The reversal of 21397991453 is 35419979312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15204616249 + 6193375204 = 123307^2 + 78698^2 .

It is a cyclic number.

It is not a de Polignac number, because 21397991453 - 2² = 21397991449 is a prime.

It is a super-2 number, since 2×21397991453² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21397991395 and 21397991404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21397991413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10698995726 + 10698995727.

It is an arithmetic number, because the mean of its divisors is an integer number (10698995727).

Almost surely, 2^21397991453 is an apocalyptic number.

It is an amenable number.

21397991453 is a deficient number, since it is larger than the sum of its proper divisors (1).

21397991453 is an equidigital number, since it uses as much as digits as its factorization.

21397991453 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1837080, while the sum is 53.

The spelling of 21397991453 in words is "twenty-one billion, three hundred ninety-seven million, nine hundred ninety-one thousand, four hundred fifty-three".