21697421959 has 4 divisors (see below), whose sum is σ = 21702091720. Its totient is φ = 21692752200.

The previous prime is 21697421957. The next prime is 21697421971. The reversal of 21697421959 is 95912479612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21697421959 - 2¹ = 21697421957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21697421957) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2327904 + ... + 2337205.

It is an arithmetic number, because the mean of its divisors is an integer number (5425522930).

Almost surely, 2^21697421959 is an apocalyptic number.

21697421959 is a deficient number, since it is larger than the sum of its proper divisors (4669761).

21697421959 is an equidigital number, since it uses as much as digits as its factorization.

21697421959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4669760.

The product of its digits is 2449440, while the sum is 55.

The spelling of 21697421959 in words is "twenty-one billion, six hundred ninety-seven million, four hundred twenty-one thousand, nine hundred fifty-nine".