21778955 has 16 divisors (see below), whose sum is σ = 30189024. Its totient is φ = 14906880.

The previous prime is 21778949. The next prime is 21778969. The reversal of 21778955 is 55987712.

It is not a de Polignac number, because 21778955 - 2²⁴ = 5001739 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10712 + ... + 12581.

It is an arithmetic number, because the mean of its divisors is an integer number (1886814).

Almost surely, 2^21778955 is an apocalyptic number.

21778955 is a deficient number, since it is larger than the sum of its proper divisors (8410069).

21778955 is a wasteful number, since it uses less digits than its factorization.

21778955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23326.

The product of its digits is 176400, while the sum is 44.

The square root of 21778955 is about 4666.7927959146. The cubic root of 21778955 is about 279.2623227061.

The spelling of 21778955 in words is "twenty-one million, seven hundred seventy-eight thousand, nine hundred fifty-five".