2157867421 has 2 divisors, whose sum is σ = 2157867422. Its totient is φ = 2157867420.

The previous prime is 2157867403. The next prime is 2157867457. The reversal of 2157867421 is 1247687512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1248844921 + 909022500 = 35339^2 + 30150^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2157867421 is a prime.

It is a super-2 number, since 2×2157867421² = 9312783613226382482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2157867401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1078933710 + 1078933711.

It is an arithmetic number, because the mean of its divisors is an integer number (1078933711).

Almost surely, 2^2157867421 is an apocalyptic number.

It is an amenable number.

2157867421 is a deficient number, since it is larger than the sum of its proper divisors (1).

2157867421 is an equidigital number, since it uses as much as digits as its factorization.

2157867421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 188160, while the sum is 43.

The square root of 2157867421 is about 46452.8515916946. The cubic root of 2157867421 is about 1292.2352570686.

The spelling of 2157867421 in words is "two billion, one hundred fifty-seven million, eight hundred sixty-seven thousand, four hundred twenty-one".