21663992778 has 32 divisors (see below), whose sum is σ = 43776027072. Its totient is φ = 7146720000.

The previous prime is 21663992773. The next prime is 21663992783. The reversal of 21663992778 is 87729936612.

It is an interprime number because it is at equal distance from previous prime (21663992773) and next prime (21663992783).

It is not an unprimeable number, because it can be changed into a prime (21663992771) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1691025 + ... + 1703787.

It is an arithmetic number, because the mean of its divisors is an integer number (1368000846).

Almost surely, 2^21663992778 is an apocalyptic number.

21663992778 is an abundant number, since it is smaller than the sum of its proper divisors (22112034294).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21663992778 is a wasteful number, since it uses less digits than its factorization.

21663992778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15670.

The product of its digits is 13716864, while the sum is 60.

The spelling of 21663992778 in words is "twenty-one billion, six hundred sixty-three million, nine hundred ninety-two thousand, seven hundred seventy-eight".