21457207 has 2 divisors, whose sum is σ = 21457208. Its totient is φ = 21457206.

The previous prime is 21457201. The next prime is 21457253. The reversal of 21457207 is 70275412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21457207 - 2³ = 21457199 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21457201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728603 + 10728604.

It is an arithmetic number, because the mean of its divisors is an integer number (10728604).

Almost surely, 2^21457207 is an apocalyptic number.

21457207 is a deficient number, since it is larger than the sum of its proper divisors (1).

21457207 is an equidigital number, since it uses as much as digits as its factorization.

21457207 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21457207 is about 4632.1924614593. The cubic root of 21457207 is about 277.8802815952.

The spelling of 21457207 in words is "twenty-one million, four hundred fifty-seven thousand, two hundred seven".