51909981 has 8 divisors (see below), whose sum is σ = 69311424. Its totient is φ = 34557600.

The previous prime is 51909953. The next prime is 51909989. The reversal of 51909981 is 18990915.

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

It is not a de Polignac number, because 51909981 - 2⁶ = 51909917 is a prime.

It is a super-2 number, since 2×51909981² = 5389292254840722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51909989) 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, 9720 + ... + 14081.

It is an arithmetic number, because the mean of its divisors is an integer number (8663928).

Almost surely, 2^51909981 is an apocalyptic number.

It is an amenable number.

51909981 is a deficient number, since it is larger than the sum of its proper divisors (17401443).

51909981 is a wasteful number, since it uses less digits than its factorization.

51909981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24531.

The product of its (nonzero) digits is 29160, while the sum is 42.

The square root of 51909981 is about 7204.8581526634. The cubic root of 51909981 is about 373.0356086344.

The spelling of 51909981 in words is "fifty-one million, nine hundred nine thousand, nine hundred eighty-one".