19451893921 has 2 divisors, whose sum is σ = 19451893922. Its totient is φ = 19451893920.

The previous prime is 19451893847. The next prime is 19451893939. The reversal of 19451893921 is 12939815491.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17066548321 + 2385345600 = 130639^2 + 48840^2 .

It is a cyclic number.

It is not a de Polignac number, because 19451893921 - 2⁷ = 19451893793 is a prime.

It is a super-2 number, since 2×19451893921² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (19451893991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9725946960 + 9725946961.

It is an arithmetic number, because the mean of its divisors is an integer number (9725946961).

Almost surely, 2^19451893921 is an apocalyptic number.

It is an amenable number.

19451893921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19451893921 is an equidigital number, since it uses as much as digits as its factorization.

19451893921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 699840, while the sum is 52.

The spelling of 19451893921 in words is "nineteen billion, four hundred fifty-one million, eight hundred ninety-three thousand, nine hundred twenty-one".