21978415945 has 8 divisors (see below), whose sum is σ = 26391335040. Its totient is φ = 17571242160.

The previous prime is 21978415939. The next prime is 21978415967. The reversal of 21978415945 is 54951487912.

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

It is not a de Polignac number, because 21978415945 - 2¹³ = 21978407753 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1427905 + ... + 1443214.

It is an arithmetic number, because the mean of its divisors is an integer number (3298916880).

Almost surely, 2^21978415945 is an apocalyptic number.

It is an amenable number.

21978415945 is a deficient number, since it is larger than the sum of its proper divisors (4412919095).

21978415945 is a wasteful number, since it uses less digits than its factorization.

21978415945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2872655.

The product of its digits is 3628800, while the sum is 55.

The spelling of 21978415945 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred fifteen thousand, nine hundred forty-five".