1221400620 has 432 divisors, whose sum is σ = 4424469504. Its totient is φ = 282268800.

The previous prime is 1221400603. The next prime is 1221400637. The reversal of 1221400620 is 260041221.

1221400620 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 40 + 0 + 620 = 666.

It is an interprime number because it is at equal distance from previous prime (1221400603) and next prime (1221400637).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 1221400593 and 1221400602.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 18229827 + ... + 18229893.

Almost surely, 2^1221400620 is an apocalyptic number.

1221400620 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221400620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2212234752).

1221400620 is an abundant number, since it is smaller than the sum of its proper divisors (3203068884).

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

1221400620 is a wasteful number, since it uses less digits than its factorization.

1221400620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 119 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 1221400620 is about 34948.5424588780. The cubic root of 1221400620 is about 1068.9384819933.

Adding to 1221400620 its reverse (260041221), we get a palindrome (1481441841).

The spelling of 1221400620 in words is "one billion, two hundred twenty-one million, four hundred thousand, six hundred twenty".