1919403721 has 9 divisors (see below), whose sum is σ = 1937937351. Its totient is φ = 1901046912.

The previous prime is 1919403713. The next prime is 1919403727. The reversal of 1919403721 is 1273049191.

The square root of 1919403721 is 43811.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 465049225 + 1454354496 = 21565^2 + 38136^2 .

It is not a de Polignac number, because 1919403721 - 2³ = 1919403713 is a prime.

It is a super-2 number, since 2×1919403721² = 7368221288377291682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1919403727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 8455410 + ... + 8455636.

Almost surely, 2^1919403721 is an apocalyptic number.

1919403721 is the 43811-st square number.

1919403721 is the 21906-th centered octagonal number.

It is an amenable number.

1919403721 is a deficient number, since it is larger than the sum of its proper divisors (18533630).

1919403721 is an frugal number, since it uses more digits than its factorization.

1919403721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 840 (or 420 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 37.

The cubic root of 1919403721 is about 1242.7643239562.

The spelling of 1919403721 in words is "one billion, nine hundred nineteen million, four hundred three thousand, seven hundred twenty-one".