21945578 has 8 divisors (see below), whose sum is σ = 33721380. Its totient is φ = 10705120.

The previous prime is 21945577. The next prime is 21945587. The reversal of 21945578 is 87554912.

It can be written as a sum of positive squares in 2 ways, for example, as 21557449 + 388129 = 4643^2 + 623^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is not an unprimeable number, because it can be changed into a prime (21945577) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133733 + ... + 133896.

Almost surely, 2^21945578 is an apocalyptic number.

21945578 is a deficient number, since it is larger than the sum of its proper divisors (11775802).

21945578 is a wasteful number, since it uses less digits than its factorization.

21945578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267672.

The product of its digits is 100800, while the sum is 41.

The square root of 21945578 is about 4684.6107629130. The cubic root of 21945578 is about 279.9726929152.

The spelling of 21945578 in words is "twenty-one million, nine hundred forty-five thousand, five hundred seventy-eight".