72051781 has 16 divisors (see below), whose sum is σ = 78912000. Its totient is φ = 65534400.

The previous prime is 72051779. The next prime is 72051787. The reversal of 72051781 is 18715027.

72051781 = T₁₁₉₈ + T₁₁₉₉ + ... + T₁₂₉₀.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 72051781 - 2¹ = 72051779 is a prime.

It is a super-2 number, since 2×72051781² = 10382918290543922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72051787) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87351 + ... + 88171.

It is an arithmetic number, because the mean of its divisors is an integer number (4932000).

Almost surely, 2^72051781 is an apocalyptic number.

It is an amenable number.

72051781 is a deficient number, since it is larger than the sum of its proper divisors (6860219).

72051781 is a wasteful number, since it uses less digits than its factorization.

72051781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1020.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 72051781 is about 8488.3320505268. The cubic root of 72051781 is about 416.1164711012.

The spelling of 72051781 in words is "seventy-two million, fifty-one thousand, seven hundred eighty-one".