21461281778 has 4 divisors (see below), whose sum is σ = 32191922670. Its totient is φ = 10730640888.

The previous prime is 21461281747. The next prime is 21461281783. The reversal of 21461281778 is 87718216412.

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

It can be written as a sum of positive squares in only one way, i.e., 21419200609 + 42081169 = 146353^2 + 6487^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5365320443 + ... + 5365320446.

Almost surely, 2^21461281778 is an apocalyptic number.

21461281778 is a deficient number, since it is larger than the sum of its proper divisors (10730640892).

21461281778 is a wasteful number, since it uses less digits than its factorization.

21461281778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10730640891.

The product of its digits is 301056, while the sum is 47.

The spelling of 21461281778 in words is "twenty-one billion, four hundred sixty-one million, two hundred eighty-one thousand, seven hundred seventy-eight".