21206951 has 2 divisors, whose sum is σ = 21206952. Its totient is φ = 21206950.

The previous prime is 21206947. The next prime is 21206953. The reversal of 21206951 is 15960212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21206951 - 2² = 21206947 is a prime.

Together with 21206953, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21206951.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21206953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603475 + 10603476.

It is an arithmetic number, because the mean of its divisors is an integer number (10603476).

Almost surely, 2^21206951 is an apocalyptic number.

21206951 is a deficient number, since it is larger than the sum of its proper divisors (1).

21206951 is an equidigital number, since it uses as much as digits as its factorization.

21206951 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21206951 is about 4605.1005417906. The cubic root of 21206951 is about 276.7957458040.

The spelling of 21206951 in words is "twenty-one million, two hundred six thousand, nine hundred fifty-one".