21976409 has 32 divisors (see below), whose sum is σ = 28498176. Its totient is φ = 16485120.

The previous prime is 21976399. The next prime is 21976421. The reversal of 21976409 is 90467912.

It is a cyclic number.

It is not a de Polignac number, because 21976409 - 2⁸ = 21976153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21976439) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 205334 + ... + 205440.

It is an arithmetic number, because the mean of its divisors is an integer number (890568).

Almost surely, 2^21976409 is an apocalyptic number.

It is an amenable number.

21976409 is a deficient number, since it is larger than the sum of its proper divisors (6521767).

21976409 is a wasteful number, since it uses less digits than its factorization.

21976409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 225.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 21976409 is about 4687.9002762431. The cubic root of 21976409 is about 280.1037413205.

The spelling of 21976409 in words is "twenty-one million, nine hundred seventy-six thousand, four hundred nine".