19957621 has 2 divisors, whose sum is σ = 19957622. Its totient is φ = 19957620.

The previous prime is 19957607. The next prime is 19957631. The reversal of 19957621 is 12675991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19580625 + 376996 = 4425^2 + 614^2 .

It is an emirp because it is prime and its reverse (12675991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19957621 - 2⁷ = 19957493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19957631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9978810 + 9978811.

It is an arithmetic number, because the mean of its divisors is an integer number (9978811).

Almost surely, 2^19957621 is an apocalyptic number.

It is an amenable number.

19957621 is a deficient number, since it is larger than the sum of its proper divisors (1).

19957621 is an equidigital number, since it uses as much as digits as its factorization.

19957621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34020, while the sum is 40.

The square root of 19957621 is about 4467.3953261380. The cubic root of 19957621 is about 271.2499022418.

The spelling of 19957621 in words is "nineteen million, nine hundred fifty-seven thousand, six hundred twenty-one".