1551621989 has 2 divisors, whose sum is σ = 1551621990. Its totient is φ = 1551621988.

The previous prime is 1551621983. The next prime is 1551622027. The reversal of 1551621989 is 9891261551.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1274133025 + 277488964 = 35695^2 + 16658^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1551621989 is a prime.

It is a super-2 number, since 2×1551621989² = 4815061593496632242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1551621983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 775810994 + 775810995.

It is an arithmetic number, because the mean of its divisors is an integer number (775810995).

Almost surely, 2^1551621989 is an apocalyptic number.

It is an amenable number.

1551621989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1551621989 is an equidigital number, since it uses as much as digits as its factorization.

1551621989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 194400, while the sum is 47.

The square root of 1551621989 is about 39390.6332647750. The cubic root of 1551621989 is about 1157.6980680385.

The spelling of 1551621989 in words is "one billion, five hundred fifty-one million, six hundred twenty-one thousand, nine hundred eighty-nine".