21942917 has 4 divisors (see below), whose sum is σ = 22028556. Its totient is φ = 21857280.

The previous prime is 21942911. The next prime is 21942919. The reversal of 21942917 is 71924912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12737761 + 9205156 = 3569^2 + 3034^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21942917 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 (21942911) 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, 42434 + ... + 42947.

It is an arithmetic number, because the mean of its divisors is an integer number (5507139).

Almost surely, 2^21942917 is an apocalyptic number.

It is an amenable number.

21942917 is a deficient number, since it is larger than the sum of its proper divisors (85639).

21942917 is an equidigital number, since it uses as much as digits as its factorization.

21942917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85638.

The product of its digits is 9072, while the sum is 35.

The square root of 21942917 is about 4684.3267392444. The cubic root of 21942917 is about 279.9613764752.

The spelling of 21942917 in words is "twenty-one million, nine hundred forty-two thousand, nine hundred seventeen".