20897951 has 4 divisors (see below), whose sum is σ = 21618600. Its totient is φ = 20177304.

The previous prime is 20897923. The next prime is 20897969. The reversal of 20897951 is 15979802.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20897951 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20897899 and 20897908.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20897551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 360281 + ... + 360338.

It is an arithmetic number, because the mean of its divisors is an integer number (5404650).

Almost surely, 2^20897951 is an apocalyptic number.

20897951 is a deficient number, since it is larger than the sum of its proper divisors (720649).

20897951 is an equidigital number, since it uses as much as digits as its factorization.

20897951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 720648.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 20897951 is about 4571.4276763392. The cubic root of 20897951 is about 275.4447942366. Note that the first 3 decimals are identical.

The spelling of 20897951 in words is "twenty million, eight hundred ninety-seven thousand, nine hundred fifty-one".