19973521 has 4 divisors (see below), whose sum is σ = 21148452. Its totient is φ = 18798592.

The previous prime is 19973501. The next prime is 19973539. The reversal of 19973521 is 12537991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12537991 = 1031 ⋅12161.

It can be written as a sum of positive squares in 2 ways, for example, as 16321600 + 3651921 = 4040^2 + 1911^2 .

It is a cyclic number.

It is not a de Polignac number, because 19973521 - 2¹¹ = 19971473 is a prime.

It is a super-2 number, since 2×19973521² = 797883082274882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19973501) 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, 587440 + ... + 587473.

It is an arithmetic number, because the mean of its divisors is an integer number (5287113).

Almost surely, 2^19973521 is an apocalyptic number.

It is an amenable number.

19973521 is a deficient number, since it is larger than the sum of its proper divisors (1174931).

19973521 is a wasteful number, since it uses less digits than its factorization.

19973521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1174930.

The product of its digits is 17010, while the sum is 37.

The square root of 19973521 is about 4469.1745322822. The cubic root of 19973521 is about 271.3219169810.

The spelling of 19973521 in words is "nineteen million, nine hundred seventy-three thousand, five hundred twenty-one".