1971621 has 20 divisors (see below), whose sum is σ = 2986764. Its totient is φ = 1296000.

The previous prime is 1971601. The next prime is 1971637. The reversal of 1971621 is 1261791.

It can be written as a sum of positive squares in 2 ways, for example, as 1726596 + 245025 = 1314^2 + 495^2 .

It is not a de Polignac number, because 1971621 - 2⁵ = 1971589 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

1971621 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1971601) 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 19 ways as a sum of consecutive naturals, for example, 8061 + ... + 8301.

2^1971621 is an apocalyptic number.

It is an amenable number.

1971621 is a deficient number, since it is larger than the sum of its proper divisors (1015143).

1971621 is a wasteful number, since it uses less digits than its factorization.

1971621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 354 (or 345 counting only the distinct ones).

The product of its digits is 756, while the sum is 27.

The square root of 1971621 is about 1404.1442233617. The cubic root of 1971621 is about 125.3933422898.

The spelling of 1971621 in words is "one million, nine hundred seventy-one thousand, six hundred twenty-one".