1221781 has 8 divisors (see below), whose sum is σ = 1346400. Its totient is φ = 1099440.

The previous prime is 1221767. The next prime is 1221791. The reversal of 1221781 is 1871221.

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

It is a cyclic number.

It is not a de Polignac number, because 1221781 - 2⁵ = 1221749 is a prime.

It is a super-2 number, since 2×1221781² = 2985497623922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221751) 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, 690 + ... + 1708.

It is an arithmetic number, because the mean of its divisors is an integer number (168300).

2^1221781 is an apocalyptic number.

1221781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221781 is a deficient number, since it is larger than the sum of its proper divisors (124619).

1221781 is a wasteful number, since it uses less digits than its factorization.

1221781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1139.

The product of its digits is 224, while the sum is 22.

The square root of 1221781 is about 1105.3420285143. The cubic root of 1221781 is about 106.9049436748.

It can be divided in two parts, 1221 and 781, that added together give a palindrome (2002).

The spelling of 1221781 in words is "one million, two hundred twenty-one thousand, seven hundred eighty-one".