21978670 has 16 divisors (see below), whose sum is σ = 45213408. Its totient is φ = 7535520.

The previous prime is 21978661. The next prime is 21978673. The reversal of 21978670 is 7687912.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 156921 + ... + 157060.

It is an arithmetic number, because the mean of its divisors is an integer number (2825838).

Almost surely, 2^21978670 is an apocalyptic number.

21978670 is an abundant number, since it is smaller than the sum of its proper divisors (23234738).

21978670 is a wasteful number, since it uses less digits than its factorization.

21978670 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 313995.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 21978670 is about 4688.1414227815. The cubic root of 21978670 is about 280.1133469669.

The spelling of 21978670 in words is "twenty-one million, nine hundred seventy-eight thousand, six hundred seventy".