21971939 has 8 divisors (see below), whose sum is σ = 25379568. Its totient is φ = 18799360.

The previous prime is 21971933. The next prime is 21971947. The reversal of 21971939 is 93917912.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21971939 is a prime.

It is a super-2 number, since 2×21971939² = 965532206839442, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21971896 and 21971905.

It is not an unprimeable number, because it can be changed into a prime (21971933) 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, 58562 + ... + 58935.

It is an arithmetic number, because the mean of its divisors is an integer number (3172446).

Almost surely, 2^21971939 is an apocalyptic number.

21971939 is a deficient number, since it is larger than the sum of its proper divisors (3407629).

21971939 is a wasteful number, since it uses less digits than its factorization.

21971939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117525.

The product of its digits is 30618, while the sum is 41.

The square root of 21971939 is about 4687.4234927090. The cubic root of 21971939 is about 280.0847490059.

The spelling of 21971939 in words is "twenty-one million, nine hundred seventy-one thousand, nine hundred thirty-nine".