15181981 has 2 divisors, whose sum is σ = 15181982. Its totient is φ = 15181980.

The previous prime is 15181979. The next prime is 15182021. The reversal of 15181981 is 18918151.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13579225 + 1602756 = 3685^2 + 1266^2 .

It is a cyclic number.

It is not a de Polignac number, because 15181981 - 2¹ = 15181979 is a prime.

It is a super-2 number, since 2×15181981² = 460985094168722, which contains 22 as substring.

Together with 15181979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15181921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7590990 + 7590991.

It is an arithmetic number, because the mean of its divisors is an integer number (7590991).

Almost surely, 2^15181981 is an apocalyptic number.

It is an amenable number.

15181981 is a deficient number, since it is larger than the sum of its proper divisors (1).

15181981 is an equidigital number, since it uses as much as digits as its factorization.

15181981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 34.

The square root of 15181981 is about 3896.4061646599. The cubic root of 15181981 is about 247.6145427711.

The spelling of 15181981 in words is "fifteen million, one hundred eighty-one thousand, nine hundred eighty-one".