21642937 has 2 divisors, whose sum is σ = 21642938. Its totient is φ = 21642936.

The previous prime is 21642923. The next prime is 21642941. The reversal of 21642937 is 73924612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21427641 + 215296 = 4629^2 + 464^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21642937 is a prime.

It is not a weakly prime, because it can be changed into another prime (21642337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821468 + 10821469.

It is an arithmetic number, because the mean of its divisors is an integer number (10821469).

Almost surely, 2^21642937 is an apocalyptic number.

It is an amenable number.

21642937 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642937 is an equidigital number, since it uses as much as digits as its factorization.

21642937 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 34.

The square root of 21642937 is about 4652.1970078663. The cubic root of 21642937 is about 278.6797411189.

The spelling of 21642937 in words is "twenty-one million, six hundred forty-two thousand, nine hundred thirty-seven".