21011957 has 2 divisors, whose sum is σ = 21011958. Its totient is φ = 21011956.

The previous prime is 21011951. The next prime is 21011959. The reversal of 21011957 is 75911012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17648401 + 3363556 = 4201^2 + 1834^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011957 - 2²⁰ = 19963381 is a prime.

Together with 21011959, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505978 + 10505979.

It is an arithmetic number, because the mean of its divisors is an integer number (10505979).

Almost surely, 2^21011957 is an apocalyptic number.

It is an amenable number.

21011957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011957 is an equidigital number, since it uses as much as digits as its factorization.

21011957 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 630, while the sum is 26.

The square root of 21011957 is about 4583.8801249596. The cubic root of 21011957 is about 275.9447703323.

Adding to 21011957 its reverse (75911012), we get a palindrome (96922969).

It can be divided in two parts, 210 and 11957, that added together give a cube (12167 = 23³).

The spelling of 21011957 in words is "twenty-one million, eleven thousand, nine hundred fifty-seven".