21908487994 has 8 divisors (see below), whose sum is σ = 33482783700. Its totient is φ = 10747560096.

The previous prime is 21908487973. The next prime is 21908488033. The reversal of 21908487994 is 49978480912.

It can be written as a sum of positive squares in 2 ways, for example, as 20864358025 + 1044129969 = 144445^2 + 32313^2 .

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

It is a super-3 number, since 3×21908487994³ (a number of 32 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 103341819 + ... + 103342030.

Almost surely, 2^21908487994 is an apocalyptic number.

21908487994 is a deficient number, since it is larger than the sum of its proper divisors (11574295706).

21908487994 is a wasteful number, since it uses less digits than its factorization.

21908487994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206683904.

The product of its (nonzero) digits is 10450944, while the sum is 61.

The spelling of 21908487994 in words is "twenty-one billion, nine hundred eight million, four hundred eighty-seven thousand, nine hundred ninety-four".