21401957 has 2 divisors, whose sum is σ = 21401958. Its totient is φ = 21401956.

The previous prime is 21401953. The next prime is 21401987. The reversal of 21401957 is 75910412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17297281 + 4104676 = 4159^2 + 2026^2 .

It is a cyclic number.

It is not a de Polignac number, because 21401957 - 2² = 21401953 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21401951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700978 + 10700979.

It is an arithmetic number, because the mean of its divisors is an integer number (10700979).

Almost surely, 2^21401957 is an apocalyptic number.

It is an amenable number.

21401957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21401957 is an equidigital number, since it uses as much as digits as its factorization.

21401957 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 21401957 is about 4626.2249188728. The cubic root of 21401957 is about 277.6415726495.

The spelling of 21401957 in words is "twenty-one million, four hundred one thousand, nine hundred fifty-seven".