21538961999 has 8 divisors (see below), whose sum is σ = 22065563520. Its totient is φ = 21013528536.

The previous prime is 21538961993. The next prime is 21538962019. The reversal of 21538961999 is 99916983512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21538961999 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538961993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 254627 + ... + 328500.

It is an arithmetic number, because the mean of its divisors is an integer number (2758195440).

Almost surely, 2^21538961999 is an apocalyptic number.

21538961999 is a deficient number, since it is larger than the sum of its proper divisors (526601521).

21538961999 is an equidigital number, since it uses as much as digits as its factorization.

21538961999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 584029.

The product of its digits is 9447840, while the sum is 62.

The spelling of 21538961999 in words is "twenty-one billion, five hundred thirty-eight million, nine hundred sixty-one thousand, nine hundred ninety-nine".