20749251 has 8 divisors (see below), whose sum is σ = 27688960. Its totient is φ = 13821192.

The previous prime is 20749241. The next prime is 20749259. The reversal of 20749251 is 15294702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20749251 - 2⁶ = 20749187 is a prime.

It is a super-2 number, since 2×20749251² = 861062834122002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20749259) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2910 + ... + 7068.

It is an arithmetic number, because the mean of its divisors is an integer number (3461120).

Almost surely, 2^20749251 is an apocalyptic number.

20749251 is a deficient number, since it is larger than the sum of its proper divisors (6939709).

20749251 is a wasteful number, since it uses less digits than its factorization.

20749251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5825.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 20749251 is about 4555.1345753995. The cubic root of 20749251 is about 274.7899266175.

It can be divided in two parts, 2074 and 9251, that added together give a triangular number (11325 = T₁₅₀).

The spelling of 20749251 in words is "twenty million, seven hundred forty-nine thousand, two hundred fifty-one".