21878554 has 4 divisors (see below), whose sum is σ = 32817834. Its totient is φ = 10939276.

The previous prime is 21878531. The next prime is 21878567. The reversal of 21878554 is 45587812.

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., 21874329 + 4225 = 4677^2 + 65^2 .

It is a super-2 number, since 2×21878554² = 957342250261832, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5469637 + ... + 5469640.

Almost surely, 2^21878554 is an apocalyptic number.

21878554 is a deficient number, since it is larger than the sum of its proper divisors (10939280).

21878554 is a wasteful number, since it uses less digits than its factorization.

21878554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10939279.

The product of its digits is 89600, while the sum is 40.

The square root of 21878554 is about 4677.4516566182. The cubic root of 21878554 is about 279.6873806830.

The spelling of 21878554 in words is "twenty-one million, eight hundred seventy-eight thousand, five hundred fifty-four".