21442657 has 2 divisors, whose sum is σ = 21442658. Its totient is φ = 21442656.

The previous prime is 21442649. The next prime is 21442667. The reversal of 21442657 is 75624412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19927296 + 1515361 = 4464^2 + 1231^2 .

It is a cyclic number.

It is not a de Polignac number, because 21442657 - 2³ = 21442649 is a prime.

It is not a weakly prime, because it can be changed into another prime (21442637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10721328 + 10721329.

It is an arithmetic number, because the mean of its divisors is an integer number (10721329).

Almost surely, 2^21442657 is an apocalyptic number.

It is an amenable number.

21442657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21442657 is an equidigital number, since it uses as much as digits as its factorization.

21442657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 31.

The square root of 21442657 is about 4630.6216645284. The cubic root of 21442657 is about 277.8174577567.

The spelling of 21442657 in words is "twenty-one million, four hundred forty-two thousand, six hundred fifty-seven".