921998557 has 2 divisors, whose sum is σ = 921998558. Its totient is φ = 921998556.

The previous prime is 921998549. The next prime is 921998593. The reversal of 921998557 is 755899129.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 917241796 + 4756761 = 30286^2 + 2181^2 .

It is a cyclic number.

It is not a de Polignac number, because 921998557 - 2³ = 921998549 is a prime.

It is a super-2 number, since 2×921998557² = 1700162678220164498, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 921998498 and 921998507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (921998507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 460999278 + 460999279.

It is an arithmetic number, because the mean of its divisors is an integer number (460999279).

Almost surely, 2^921998557 is an apocalyptic number.

It is an amenable number.

921998557 is a deficient number, since it is larger than the sum of its proper divisors (1).

921998557 is an equidigital number, since it uses as much as digits as its factorization.

921998557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2041200, while the sum is 55.

The square root of 921998557 is about 30364.4291400316. The cubic root of 921998557 is about 973.2925828809.

The spelling of 921998557 in words is "nine hundred twenty-one million, nine hundred ninety-eight thousand, five hundred fifty-seven".