21778280121 has 16 divisors (see below), whose sum is σ = 31458639744. Its totient is φ = 13321762944.

The previous prime is 21778280101. The next prime is 21778280123. The reversal of 21778280121 is 12108287712.

It is not a de Polignac number, because 21778280121 - 2¹¹ = 21778278073 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a self number, because there is not a number n which added to its sum of digits gives 21778280121.

It is not an unprimeable number, because it can be changed into a prime (21778280123) 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, 1665396 + ... + 1678421.

It is an arithmetic number, because the mean of its divisors is an integer number (1966164984).

Almost surely, 2^21778280121 is an apocalyptic number.

It is an amenable number.

21778280121 is a deficient number, since it is larger than the sum of its proper divisors (9680359623).

21778280121 is a wasteful number, since it uses less digits than its factorization.

21778280121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3344000.

The product of its (nonzero) digits is 25088, while the sum is 39.

The spelling of 21778280121 in words is "twenty-one billion, seven hundred seventy-eight million, two hundred eighty thousand, one hundred twenty-one".