161221770 has 48 divisors (see below), whose sum is σ = 420972552. Its totient is φ = 42808320.

The previous prime is 161221769. The next prime is 161221771. The reversal of 161221770 is 77122161.

It is an interprime number because it is at equal distance from previous prime (161221769) and next prime (161221771).

It can be written as a sum of positive squares in 4 ways, for example, as 109683729 + 51538041 = 10473^2 + 7179^2 .

It is not an unprimeable number, because it can be changed into a prime (161221771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17974 + ... + 25406.

Almost surely, 2^161221770 is an apocalyptic number.

161221770 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

161221770 is an abundant number, since it is smaller than the sum of its proper divisors (259750782).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

161221770 is a wasteful number, since it uses less digits than its factorization.

161221770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7687 (or 7684 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 27.

The square root of 161221770 is about 12697.3134953816. The cubic root of 161221770 is about 544.2618517537.

The spelling of 161221770 in words is "one hundred sixty-one million, two hundred twenty-one thousand, seven hundred seventy".