1221639 has 8 divisors (see below), whose sum is σ = 1635312. Its totient is φ = 811200.

The previous prime is 1221631. The next prime is 1221641. The reversal of 1221639 is 9361221.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1221639 - 2³ = 1221631 is a prime.

1221639 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 289 + ... + 1589.

It is an arithmetic number, because the mean of its divisors is an integer number (204414).

2^1221639 is an apocalyptic number.

1221639 is a deficient number, since it is larger than the sum of its proper divisors (413673).

1221639 is a wasteful number, since it uses less digits than its factorization.

1221639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1617.

The product of its digits is 648, while the sum is 24.

The square root of 1221639 is about 1105.2777931362. The cubic root of 1221639 is about 106.9008018823.

The spelling of 1221639 in words is "one million, two hundred twenty-one thousand, six hundred thirty-nine".