221978431 has 2 divisors, whose sum is σ = 221978432. Its totient is φ = 221978430.

The previous prime is 221978417. The next prime is 221978461. The reversal of 221978431 is 134879122.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 221978431 - 2⁵ = 221978399 is a prime.

It is a super-2 number, since 2×221978431² = 98548847658443522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221978461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110989215 + 110989216.

It is an arithmetic number, because the mean of its divisors is an integer number (110989216).

Almost surely, 2^221978431 is an apocalyptic number.

221978431 is a deficient number, since it is larger than the sum of its proper divisors (1).

221978431 is an equidigital number, since it uses as much as digits as its factorization.

221978431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 37.

The square root of 221978431 is about 14898.9405999219. The cubic root of 221978431 is about 605.4852842036.

It can be divided in two parts, 22197 and 8431, that added together give a triangular number (30628 = T₂₄₇).

The spelling of 221978431 in words is "two hundred twenty-one million, nine hundred seventy-eight thousand, four hundred thirty-one".