21571937 has 2 divisors, whose sum is σ = 21571938. Its totient is φ = 21571936.

The previous prime is 21571933. The next prime is 21571943. The reversal of 21571937 is 73917512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19088161 + 2483776 = 4369^2 + 1576^2 .

It is a cyclic number.

It is not a de Polignac number, because 21571937 - 2² = 21571933 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21571897 and 21571906.

It is not a weakly prime, because it can be changed into another prime (21571933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10785968 + 10785969.

It is an arithmetic number, because the mean of its divisors is an integer number (10785969).

Almost surely, 2^21571937 is an apocalyptic number.

It is an amenable number.

21571937 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571937 is an equidigital number, since it uses as much as digits as its factorization.

21571937 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13230, while the sum is 35.

The square root of 21571937 is about 4644.5599360973. The cubic root of 21571937 is about 278.3746694995.

The spelling of 21571937 in words is "twenty-one million, five hundred seventy-one thousand, nine hundred thirty-seven".