20919257 has 4 divisors (see below), whose sum is σ = 21047760. Its totient is φ = 20790756.

The previous prime is 20919251. The next prime is 20919263. The reversal of 20919257 is 75291902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (20919251) and next prime (20919263).

It is a cyclic number.

It is not a de Polignac number, because 20919257 - 2⁸ = 20919001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20919251) 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, 64007 + ... + 64332.

It is an arithmetic number, because the mean of its divisors is an integer number (5261940).

Almost surely, 2^20919257 is an apocalyptic number.

It is an amenable number.

20919257 is a deficient number, since it is larger than the sum of its proper divisors (128503).

20919257 is a wasteful number, since it uses less digits than its factorization.

20919257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128502.

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 20919257 is about 4573.7574268866. The cubic root of 20919257 is about 275.5383701332.

The spelling of 20919257 in words is "twenty million, nine hundred nineteen thousand, two hundred fifty-seven".