19921157 has 4 divisors (see below), whose sum is σ = 19938240. Its totient is φ = 19904076.

The previous prime is 19921147. The next prime is 19921159. The reversal of 19921157 is 75112991.

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, and also an emirpimes, since its reverse is a distinct semiprime: 75112991 = 1223 ⋅61417.

It is a cyclic number.

It is not a de Polignac number, because 19921157 - 2¹² = 19917061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19921159) 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, 6653 + ... + 9170.

It is an arithmetic number, because the mean of its divisors is an integer number (4984560).

Almost surely, 2^19921157 is an apocalyptic number.

It is an amenable number.

19921157 is a deficient number, since it is larger than the sum of its proper divisors (17083).

19921157 is a wasteful number, since it uses less digits than its factorization.

19921157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17082.

The product of its digits is 5670, while the sum is 35.

The square root of 19921157 is about 4463.3123350265. The cubic root of 19921157 is about 271.0846038774.

The spelling of 19921157 in words is "nineteen million, nine hundred twenty-one thousand, one hundred fifty-seven".