21971407 has 4 divisors (see below), whose sum is σ = 22331656. Its totient is φ = 21611160.

The previous prime is 21971399. The next prime is 21971413. The reversal of 21971407 is 70417912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21971407 - 2³ = 21971399 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971437) 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, 180033 + ... + 180154.

It is an arithmetic number, because the mean of its divisors is an integer number (5582914).

Almost surely, 2^21971407 is an apocalyptic number.

21971407 is a deficient number, since it is larger than the sum of its proper divisors (360249).

21971407 is an equidigital number, since it uses as much as digits as its factorization.

21971407 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360248.

The product of its (nonzero) digits is 3528, while the sum is 31.

The square root of 21971407 is about 4687.3667447726. The cubic root of 21971407 is about 280.0824884515.

The spelling of 21971407 in words is "twenty-one million, nine hundred seventy-one thousand, four hundred seven".