20697951 has 4 divisors (see below), whose sum is σ = 27597272. Its totient is φ = 13798632.

The previous prime is 20697923. The next prime is 20697977. The reversal of 20697951 is 15979602.

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

It is not a de Polignac number, because 20697951 - 2¹¹ = 20695903 is a prime.

It is the 4550-th Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20697151) by changing a digit.

It is a nontrivial repunit in base 4549.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3449656 + ... + 3449661.

It is an arithmetic number, because the mean of its divisors is an integer number (6899318).

Almost surely, 2^20697951 is an apocalyptic number.

20697951 is a deficient number, since it is larger than the sum of its proper divisors (6899321).

20697951 is an equidigital number, since it uses as much as digits as its factorization.

20697951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6899320.

The product of its (nonzero) digits is 34020, while the sum is 39.

The square root of 20697951 is about 4549.5000824266. The cubic root of 20697951 is about 274.5632781681.

It can be divided in two parts, 20 and 697951, that added together give a triangular number (697971 = T₁₁₈₁).

The spelling of 20697951 in words is "twenty million, six hundred ninety-seven thousand, nine hundred fifty-one".