21215746897 has 4 divisors (see below), whose sum is σ = 21216290416. Its totient is φ = 21215203380.

The previous prime is 21215746879. The next prime is 21215746939. The reversal of 21215746897 is 79864751212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21215746897 - 2²⁷ = 21081529169 is a prime.

It is a super-3 number, since 3×21215746897³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21215743897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 208263 + ... + 292924.

It is an arithmetic number, because the mean of its divisors is an integer number (5304072604).

Almost surely, 2^21215746897 is an apocalyptic number.

It is an amenable number.

21215746897 is a deficient number, since it is larger than the sum of its proper divisors (543519).

21215746897 is an equidigital number, since it uses as much as digits as its factorization.

21215746897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 543518.

The product of its digits is 1693440, while the sum is 52.

The spelling of 21215746897 in words is "twenty-one billion, two hundred fifteen million, seven hundred forty-six thousand, eight hundred ninety-seven".