21657991399 has 8 divisors (see below), whose sum is σ = 23738878080. Its totient is φ = 19595767800.

The previous prime is 21657991393. The next prime is 21657991427. The reversal of 21657991399 is 99319975612.

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

It is a cyclic number.

It is not a de Polignac number, because 21657991399 - 2⁵ = 21657991367 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 (21657991393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4663339 + ... + 4667980.

It is an arithmetic number, because the mean of its divisors is an integer number (2967359760).

Almost surely, 2^21657991399 is an apocalyptic number.

21657991399 is a deficient number, since it is larger than the sum of its proper divisors (2080886681).

21657991399 is a wasteful number, since it uses less digits than its factorization.

21657991399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9331541.

The product of its digits is 8266860, while the sum is 61.

The spelling of 21657991399 in words is "twenty-one billion, six hundred fifty-seven million, nine hundred ninety-one thousand, three hundred ninety-nine".