21978675 has 24 divisors (see below), whose sum is σ = 40376880. Its totient is φ = 11721600.

The previous prime is 21978673. The next prime is 21978701. The reversal of 21978675 is 57687912.

It is not a de Polignac number, because 21978675 - 2¹ = 21978673 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21978675.

It is not an unprimeable number, because it can be changed into a prime (21978673) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15606 + ... + 16955.

It is an arithmetic number, because the mean of its divisors is an integer number (1682370).

Almost surely, 2^21978675 is an apocalyptic number.

21978675 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21978675 is a deficient number, since it is larger than the sum of its proper divisors (18398205).

21978675 is a wasteful number, since it uses less digits than its factorization.

21978675 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32580 (or 32569 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The square root of 21978675 is about 4688.1419560419. The cubic root of 21978675 is about 280.1133682082.

The spelling of 21978675 in words is "twenty-one million, nine hundred seventy-eight thousand, six hundred seventy-five".